A small group model was used to examine the effects of chlordiazepoxide hydrochloride on affective and behavioral hostility in a social interactive setting. Three-person groups of male volunteers completed paper-and-pencil affective-rating scales individually and interacted with each other during a ten-minute discussion period that was videotaped and scored for behavioral hostility. The results indicated that chlordiazepoxide was associated with an increase in individual affective but not behavioral hostility. However, when a frustration stimulus was presented to the group, interpersonal behavioral hostility was increased in those who received chlordiazepoxide as compared with those taking a placebo. The data suggest that increases in hostility may be a regular rather than paradoxical effect of chlordiazepoxide. However, overt hostility may only become apparent in settings of interpersonal frustration.