The article analyses the socio-demographic and political recruitment factors for the Assembly of Experts of Iran from 1983-2024. The Assembly is an electoral college that has constitutional control over the Supreme Leader of Iran, but does not use its powers. The database comprises 446 observations related to 216 persons during 5 Assemblies since 1983. The research method is a structural-biographical analysis. The results of the research show that the Iranian clergy in the Assembly is relatively stable. However, it changes in the national context regarding the political struggle and the massification of higher education. The effect of political struggle demonstrates the expansion of the share of moderate and reformist clergy, which contrasts with the early domination of the conservative faction only. The share of incumbents is quite high, too: approximately half of the Assembly members have been elected at least twice since the second Assembly; approximately a third of them have been elected at least thrice since the third assembly. The educational clerical origin refers to the seminaries of Qom and Najaf, with the minority from the seminary of Mashhad. Secular education also expands among them, achieving 20% for the fifth Assembly. The most frequent specializations received in secular institutions are law, philosophy, and theology. More than half of the members of the Assembly originate from 9 of 31 provinces only, which may be explained by the patrimonial connections of the Assembly`s leadership.