The purpose of this study was to evaluate factual knowledge changes, amounts of verbal interaction, and attitudinal changes that occurred in the area of sex education with three different groups of high school seniors. Group I consisted of 24 boys and girls, Group II of 28 girls, and Group III of 15 boys. Changes in factual knowledge were measured by two testing instruments: Sex Knowledge Inventory and A Vernereal Disease Knowledge Inventory. Amounts of verbal interaction were evaluated by means of the Flanders Interaction Analysis, and changes in attitudes were measured by two instruments developed by the investigator. The results indicated that during a sex education unit of study, high school seniors in a mixed group (boys and girls): (1) do not learn significantly more factual knowledge, (2) do have more verbal interaction, and (3) do have a more liberal change in attitudes than those students in a segregated group (boys or girls). Based on the findings of this study, the author advocated the use of mixed classes in teaching sex education to high school seniors. (JR)