This study used recently available survey data to examine trends in the rate of first union formation in the post-Soviet Central Asian republics of Kazakhstan, Kyrgyzstan, Tajikistan and Uzbekistan. For the first time, it shows that the rate of first union formation in each republic is much lower than the Soviet-era level at the end of the 1980s. These results have three implications. First, they complement the literature on Central and Eastern Europe by illustrating the scale of post-socialist demographic change in very different cultural and demographic context. Second, post-Soviet Tajikistan and Uzbekistan here provide interesting examples of countries experiencing dramatic declines in first union formation in a conservative Moslem setting and at the same time as an increase in religiosity and a decrease in female higher education enrolment. Third, more generally, they serve to illustrate profound changes in demographic behaviour during dramatic social and economic change.