Within each category of incidents, those considered relatively minor are distinguished from those considered serious as viewed by the police or other social agencies. This report also draws seven conclusions from analyses of the data presented. First, it concludes that what has in the past been called the “missing children” problem is actually a set of at least five very different, distinct problems. Each of these problems requires research, analysis, and distinctive responses. Second, many of the children in at least four of the five categories were not literally missing; caretakers knew where they were, and the problem was in recovering them. Third, because of definitional controversies and confusion about the concept of missing children, public policy should clarify the domain of this problem, decide which children and situations should be included in NISMART, and determine what they have in common and what they are to be called. Fourth, “family abduction” was apparently a significantly larger problem than previously thought based on the incidence estimates. Fifth, the “runway” problem was not apparently larger in 1988 than at the time of the last national survey in 1975. Sixth, just over 20 percent of the children who had previously been termed “runaways” should be considered “thrownaways." Seventh, there were a large number of children missing because they were lost, injured, or failed to communicate clearly to caretakers about their location or when they would be home. This report describes NISMART’s methodology. Extensive tables and figures, 100 references, and appended estimated incidence of countable children in different missing children categories and a guide to definitions