The stability of mothers' recall of age of onset of attention deficit and hyperactive behaviors was assessed over a 1-year interval. The paper reports on which behaviors have the highest stability and the stability of a psychiatric diagnosis of attention deficit hyperactive disorder using different age cut-offs. The data showed a moderate degree of stability over a 1-year period, with school-related symptoms showing the least amount of change. An argument is made for keeping the current DSM-III-R diagnostic cut-off at age 6.