The mean of self-report and observer ratings of working conditions was used to predict 3 types of well-being in 52 young workers: general well-being, job-related well-being, and spillover from work to nonwork domains. Longitudinally, job control predicted spillover. There was no strong evidence for reverse causation. Synchronously, Time 2 job stressors predicted all types of well-being, and job control predicted general well-being. Because dependent variables at Time 1 are controlled for, this indicates short-term effects. Results for stressors are in line with a stress reaction model, indicating a rather quick symptom development but reversibility. The effect of control on spillover, however, suggests a sleeper effect model, with symptoms appearing with delay.