Based on a sample drawn from Statistics Canada's Survey of Labour and Income Dynamics (SLID: 1993 to 1998 and 1996 to 2001), the study finds that young (17 to 34 years old) and single workers were more likely than older (35 to 59 years old) and married and divorced workers to participate in adult schooling and to obtain a post-secondary certificate. Workers with less than a high school education who might have the greatest need to increase their human capital investment were less likely to participate in adult education than workers with high school or more education. The study shows that male workers who obtained a post-secondary certificate while staying with the same employer generally registered higher wage and earnings gains than their counterparts who did not go back to school, regardless of age and initial level of education. On the other hand, men who obtained a certificate and switched jobs generally realized no significant return to their additional education, with the exception of young men (17 to 34 years old) who would receive significant returns to a certificate, whether they switched employer or stayed with the same employer. Obtaining a certificate generated significant wage and earnings returns for older women (aged 35 to 59) who stayed with the same employer, and significant wage returns for young women who switched employers.