OBJECTIVE To examine the relationship between parental monitoring and six negative behaviors: cigarette, alcohol, and marijuana use; depressed mood; risk taking; and lower academic grades. METHODS Survey of 3993 ninth-grade students in six school districts in southern California. METHODS The sample consisted of 1930 boys and 2063 girls, self-classified as non-Hispanic white (32%), African-American (13%), Hispanic (46%), or Asian (9%). RESULTS A relationship was found between unsupervised care after school and susceptibility to cigarette, alcohol, and marijuana use; depressed mood; risk taking; and lower academic grades. Adolescents who were unsupervised at home were slightly more likely to engage in problem behavior than those who were supervised at home. Adolescents at a neighbor's house, at school, or at a job and especially those who "hang out" were most likely to engage in problem behavior. Risk was higher if the parent had an unengaged parenting style. Although girls were less likely than boys to engage in problem behavior when supervised, as supervision decreased they were significantly more likely to have each of these problems. Family structure had little impact on risk. CONCLUSIONS Self-care, especially when it occurs outside of the home, is associated with substance use, risk taking, depressed mood, and lower academic grades.