An indenopyridine (YG19-256) and a benzothiazepin (thiazesim) were investigated in rats for possible effects on shock-induced defensive fighting, shock reactivity and locomotor activity. 2. YG19-256 significantly reduced aggression at the higher dose levels employed. Thiazesim produced no significant decrease in aggression at the dose levels used. 3. Neither compound produced any consistent effect on shock reactivity or locomotor activity.