In 1972, the governments of the PDRY and the YAR declared that they approved a future union. However, little progress was made toward unification, and relations were often strained. In 1979, simmering tensions led to fighting, which was only resolved after Arab League mediation. The goal of unity was reaffirmed by the northern and southern heads of state during a summit meeting in Kuwait in March 1979. However, that same year the PDRY began sponsoring an insurgency against the YAR. In April 1980, PDRY President Abdul Fattah Ismail resigned and went into exile. His successor, Ali Nasir Muhammad, took a less interventionist stance toward both the YAR and neighboring Oman. On January 13, 1986, a violent struggle began in Aden between Ali Nasir Muhammad and the returned Abdul Fattah Ismail and their supporters. Fighting lasted for more than a month and resulted in thousands of casualties, Ali Nasir's ouster, and Ismail's death. Some 60,000 persons, including Ali Nasir and his supporters, fled to the YAR.

In May 1988, the YAR and PDRY governments came to an understanding that considerably reduced tensions including agreement to renew discussions concerning unification, to establish a joint oil exploration area along their undefined border, to demilitarize the border, and to allow Yemenis unrestricted border passage on the basis of only a national identification card.

In November 1989, the leaders of the YAR (Ali Abdallah Saleh) and the PDRY (Ali Salim Al-Bidh) agreed on a draft unity constitution originally drawn up in 1981. The Republic of Yemen (ROY) was declared on May 22, 1990. Ali Abdallah Saleh became President, and Ali Salim Al-Bidh became Vice President.

A 30-month transitional period for completing the unification of the two political and economic systems was set. A presidential council was jointly elected by the 26-member YAR advisory council and the 17-member PDRY presidium. The presidential council appointed a Prime Minister, who formed a Cabinet. There was also a 301-seat provisional unified Parliament, consisting of 159 members from the north, 111 members from the south, and 31 independent members appointed by the chairman of the council.

A unity constitution was agreed upon in May 1990 and ratified by the populace in May 1991. It affirmed Yemen's commitment to free elections, a multiparty political system, the right to own private property, equality under the law, and respect of basic human rights. Parliamentary elections were held on April 27, 1993. International groups assisted in the organization of the elections and observed actual balloting. The resulting Parliament included 143 GPC, 69 YSP, 63 Islaah (Yemeni grouping for reform, a party composed of various tribal and religious groups), 6 Baathis, 3 Nasserists, 2 Al Haq, and 15 independents. The head of Islaah, Paramount Hashid Sheik Abdallah Bin Husayn Al-Ahmar, is the speaker of Parliament.

Islaah was invited into the ruling coalition, and the presidential council was altered to include one Islaah member. Conflicts within the coalition resulted in the self-imposed exile of Vice President Ali Salim Al-Bidh to Aden beginning in August 1993 and a deterioration in the general security situation as political rivals settled scores and tribal elements took advantage of the unsettled situation.

Haydar Abu Bakr Al-Attas (former southern Prime Minister) continued to serve as the ROY Prime Minister, but his government was ineffective due to political infighting. Continuous negotiations between northern and southern leaders resulted in the signing of the document of pledge and accord in Amman, Jordan on February 20, 1994. Despite this, clashes intensified until civil war broke out in early May 1994.

Almost all of the actual fighting in the 1994 civil war occurred in the southern part of the country despite air and missile attacks against cities and major installations in the north. Southerners sought support from neighboring states and received billions of dollars of equipment and financial assistance. The United States strongly supported Yemeni unity, but repeatedly called for a cease-fire and a return to the negotiating table. Various attempts, including by a UN special envoy, were unsuccessful to effect a cease-fire.

Southern leaders declared secession and the establishment of the Democratic Republic of Yemen (DRY) on May 21, 1994, but the DRY was not recognized by the international community. Ali Nasir Muhammad supporters greatly assisted military operations against the secessionists and Aden was captured on July 7, 1994. Other resistance quickly collapsed and thousands of southern leaders and military went into exile.

Early during the fighting, President Ali Abdallah Saleh announced a general amnesty which applied to everyone except a list of 16 persons. Most southerners returned to Yemen after a short exile.

An armed opposition was announced from Saudi Arabia, but no significant incidents within Yemen materialized. The government prepared legal cases against four southern leaders--Ali Salim Al- Bidh, HaydarAbu Bakr Al-Attas, Abd Al-Rahman Ali Al-Jifri, and Salih MunassarAl-Siyali--for misappropriation of official funds. Others on the list of 16 were told informally they could return to take advantage of the amnesty, but most remained outside Yemen. Although many of Ali Nasir Muhammad's followers were appointed to senior governmental positions (including Vice President, Chief of Staff, and Governor of Aden), Ali Nasir Muhammad himself remained abroad in Syria.

In the aftermath of the civil war, YSP leaders within Yemen reorganized the party and elected a new politburo in July 1994. However, the party remained disheartened and without its former influence. Islaah held a party convention in September 1994. The GPC did the same in June 1995.

In 1994, amendments to the unity constitution eliminated the presidential council. President Ali Abdallah Saleh was elected by Parliament on October 1, 1994 to a 5-year term. The constitution provides that henceforth the President will be elected by popular vote from at least two candidates selected by the legislature. Yemen held its first direct presidential elections in September 1999, electing President Ali Abdallah Saleh to a 5-year term in what were generally considered free and fair elections. Yemen held its second multiparty parliamentary elections in April 1997. In April 2003, the third multiparty parliamentary elections were held with improvements in voter registration for both men and women and in a generally free and fair atmosphere. Two women were elected. Constitutional amendments adopted in the summer of 2000 extended the presidential term by 2 years, thus moving the next presidential elections to 2006. The amendments also extended the parliamentary term of office to a 6-year term, thus moving elections for these seats to 2003. On February 20, 2001, a new constitutional amendment created a bicameral legislature consisting of a Shura Council (111 seats; members appointed by the president) and a House of Representatives (301 seats; members elected by popular vote).