This thesis first examines the inflows and outflows of four South Asian immigrant groups (Philippines, Chinese, Thai and Vietnamese). The data include all immigrant arrivals between 1967 and 2003. The results show that the majority male Chinese immigrants left Norway after 5 years living in Norway while most Vietnamese immigrants still live in Norway. The out-migration patterns vary by country of origin and class of admissions; immigrants from China based on work permit have the highest out-migration rates and immigrants from Vietnam reunified with refugees and family reunification has the lowest propensities to out-migrate. The thesis further studies the economic assimilation of these immigrant groups, with focus on earnings and employment by gender. The empirical analysis contrasts results from cross-sectional and longitudinal estimation models, because the cross-sectional estimator is known to be fragile to bias caused by selective out-migration or cohort effects. It is found that the immigrants from these four countries economic assimilate well during the first 15 years in the Norwegian labour market. The earnings growth for the Chinese males is overestimated in the cross-sectional model, and the analysis shows that the bias is caused by selective out-migraiton. The analysis also shows that the earnings growth for native females is understated in the cross-sectional model, and results point to the bias stemming from younger birth cohorts having higher labour market attachment. For native females, there are significant negative effects of having children on earnings. The earnings of female immigrants are less affected by having children. Over the life cycle female immigrants catch up with native women in terms of economic status and are fully integrated in the Norwegian labour market.