Specific research goals were to test the hypothesis that high O-H inmates would express less anger and aggression than medium and low O-H inmates in an experimental social interaction, to explore differences between medium and low O-H inmates, and to examine the relationships between overcontrolled hostility (as measured by Megargee's O-H scale) and catharsis (as measured in Hokanson's laboratory procedure). The independent variable, personality type, was defined by high, medium, and low O-H scores. Dependent variables included the intensity and type of feelings reported by subjects following frustration, message the subject wanted to convey to the experimenter after each frustration, and amount of time required for the subject's physiological arousal response to frustration to return to the prefrustration level. Study subjects were chosen from the inmate population of the Federal Correctional Institution in Tallahassee, Florida, a medium security institution for young offenders. It was found that high O-H subjects reported angry feelings following frustration significantly less than medium and low O-H subjects. High O-H subjects also avoided expressing high levels of anger the few times angry feelings were expressed. When frustrated, high O-H subjects reported feeling tense more often than medium and low O-H subjects, suggesting that high O-H subjects tended to overcontrol all strong emotional feelings. Message data supported the construct validity of high scores on the O-H scale as an indication of overcontrolled hostility. High O-H subjects avoided making negative, impunitive statements about themselves, in contrast to medium and low O-H groups. Medium and low O-H subjects did not differ in the manner in which they expressed angry feelings or social counterresponses following harassment. The study failed to find any relationship between the personality trait of overcontrolled hostility and physiological responses. 13 references and 3 tables