This paper investigates the key factors associated with the demand for Urban Resident Basic Medical Insurance (URBMI), which was established in 2007 and aims to cover all Chinese urban residents. Two waves of longitudinal household survey data are used, and a three-level random-intercept logit model is used for the analysis. Two different sets of explanatory variables were identified for adults and children, separately. Results suggest for both the adult and the child samples that income, health status, age and health risk behaviours are key influencing factors for basic medical insurance demand. The household head s characteristics are also significantly related to other household members medical insurance demands. Specifically, household heads who are more educated or retired are more likely to purchase medical insurance for their children. These findings suggest that an expansion of the special subsidy to the poor or, probably more important, a risk-adjusted benefit package may be needed for voluntary basic medical insurance in China. In addition, adverse selection consistently exists and is a major challenge for the sustainability of medical insurance financing. To expand insurance coverage for children, especially those under school age, special efforts (possibly through health education or health promotion) should be focused on the household head, particularly those engaging in risky health behaviours.