The content and process of incidental learning of sex role related characteristics through play behavior was explored in a study of more than 6000 toys sold by Sears, Roebuck & Company between 1900 and 1970, as represented in their mail order catalogs. Sixty percent of all toys were sex typed by Sears. The nature of the play behavior associated with each sex's toys was examined by decade. Each toy was categorized according to 13 characteristics which were thought to be related to sex role behavior. Trend analyses of characteristic clusters were presented and projections were made from these trends to create hypothetical profiles of males and females of the future. Three basic research questions posed were: (1) Are toys sex typed? (2) Are there differences in the sex typing of male toys and female toys? (3) Are there relationships between characteristics within each sex? Conclusions are affirmative in connection with all three questions. Sears catalogs are described as a reflection of the contemporary American value system, with toys such as Sears' considered to be socializing agents of the future, providing possibly valuable information about anticipated sex role behavior in the next few decades. (BF)