Journal of Population and Social Studies, Volume 22 Number 1 January 2014 : 70-86 DOI 10.14456/jpss.2014.7 70 Rural-urban Migration and Sexual Initiation of Never-married Young Adults from Kanchanaburi, Thailand Dusita Phuengsamran 1 , Aphichat Chamratrithirong 2 , Philip Guest 2 , and Mark VanLandingham 3 This study examines whether migration has an effect on young adults’ transition to becoming sexually experienced, using longitudinal data from the Migration and Health Project in Kanchanaburi, Thailand from 2005 and 2007. Survival analysis was used to explore the timing of sexual initiation of never married young adults, and Cox regression was used to examine the effect of migration on the hazard function of sexual initiation. Young adults who did not have sexual experience at T0 (2005) were followed up at T1 (2007) to examine whether they had experienced sexual initiation during the interim period. The results show that rural to urban migration was a strong factor in determining sexual initiation for both male and female never married young adults. Working, originating from urban districts and self-perception of being at risk of HIV also increased the likelihood of sexual initiation for males. Attitudes towards sex were found to have an effect as well; young females who were not sure if sex can be refused were more likely to have experienced sexual initiation compared to their male counterparts. Keywords: rural-urban migration, migration experience, migration and health, return migration, sexual initiation, HIV risk Introduction Migration has been regarded as a facilitating factor for many health risk behaviors, whether directly or indirectly, and sexual behavior is no exception. Sexual experience may be initiated through the course of other experiences, and migration may be especially likely to facilitate sexual initiation because it may create some forms of freedom, provide opportunities, and enhance the feasibility of having sex. 1 Institute for Population and Social Research, Mahidol University, Thailand. Email: dusita.phueng@gmail.com 2 Institute for Population and Social Research, Mahidol University, Thailand. 3 Department of Global Health Systems and Development, Tulane University School of Public Health and Tropical Medicine, USA. The initial stage of this research was conducted with the support of the Wellcome Trust-IPSR Scholarship (2008-2009). It was completed with the support of the Royal Golden Jubilee Ph.D. Scholarship (2009-2011). The authors would like to thank the Migration and Health Project, by the Institute for Population and Social Research, Mahidol University, Thailand and the International Health and Development Faculty, School of Public Health and Tropical Medicine of Tulane University in New Orleans, LA, USA, for granting permission to use the data. Published online: 16 June 2014