This paper describes research on intrahousehold interactions, based on results of an activity-based time allocation model. The paper describes a joint time-allocation model that explicitly considers a child in addition to parents. It analyzes activity duration as well as activity type. This model was formulated as a nonlinear Tobit model for econometric analysis. The model parameters were estimated with data from a household timeallocation survey completed during 2003 in Toyama, Japan. Two models were estimated with the sample data sets: one for weekdays and one for weekend days. The results indicate that social and cultural backgrounds relating to the husband's preference of child gender, household childcare role sharing between husband and wife, and the husband's immersion in work influence the household interactions significantly. The paper presents a summary of model results, conclusions, and recommendations for further research.