Parents, social service workers, and medical personnel failed to differ in the amount of time they estimated that children of 11 differing ages should be left without adult supervision within 5 different supervision domains. More hazardous circumstances dramatically reduced the amount of time respondents said children should be left unsupervised. Amount of unsupervised time increased with age, with clear developmental cutoffs that varied by level and type of risk. When the moderate center of the distribution was examined, 3 clear areas of consensus emerged. For most domains, constant supervision was recommended for preschool children. For early elementary school children, nearly constant (0-5 min without supervision) or close (0-15 min without supervision) supervision was recommended in safer locations, with constant supervision still recommended in high-risk situations. Only with older children was there an absence of consensus regarding supervision. The implications of these results for future injury prevention research are discussed.