A survey of 197 cognitive aging studies revealed infrequent use of structured health assessments and random recruitment. In this study, a health screening questionnarie developed to identify subjects with medical problems that might impair cognition was administered to 315 adults aged 60 and older who were recruited by random digit dialing. On the basis of self-reported medical problems, 35% of the subjects were excluded. Those excluded were older (p less than .001) and tended to be male but did not differ in education from those who passed the screening. Subjects who passed the screening and decided to participate in a neuropsychological research project were younger (p less than .001), better educated (p less than .001), and more likely to be male (p less than .001) than nonparticipants. These findings suggest that careful assessment, selection, and description of subjects is needed to aid interpretation of cognitive aging research. Further attention to health status is needed to aid interpretation of cognitive aging research. Although random recruitment of the elderly is feasible, obtaining representative samples may require stratification on demographic variables.