This paper contributes to the recent interest in household decisions in activity-based analysis. It focuses on the joint participation of male-female heads of household in nonwork activities and attempts to model the timing and duration decisions of these activities by using decision tree induction. The data used originate from the 2004 National Travel Survey in the Netherlands. The results show that activity type has the most significant influence in both models. In addition, time availability for nonwork activities during morning off-peak periods has a strong influence on start-time decisions. The results also suggest a strong influence of duration decisions on start-time decisions. Overall, modeling household decisions for the timing and duration of joint activity participation is shown to have some clear advantages.