Prosecutorial and judicial case files of 206 persons convicted of leftist terrorist acts between 1971 and 1980 were examined. Their offenses comprised participation in terrorist assaults on persons or facilities, as well as offenses performed to promote a terrorist group or support its violent activities. The biographical factors studied included sex, profession of parents, education, professional activity, marital status, former criminal record, and age at the time of the offense. Females comprised 26 percent of the subjects -- a higher percentage than the 15-percent female contingent of the nonterrorist offender population. Compared to common criminals, the terrorists as a group also had parents of higher socioeconomic standing and were themselves better educated. They differed little from other offenders in terms of age and marital status. The perpetrators of terrorist attacks, however, possessed medium educational levels, held nonprestigious jobs, came from lower middle-class or disadvantaged backgrounds, and had prior criminal records. Those convicted for supportive involvement with terrorist groups had characteristics popularly associated with the perpetrators of terrorist violence -- youth (age 20 to 30) and university backgrounds (study or teaching). Persons convicted of complicity or support of terrorist attacks were more frequently older and married, highly educated, in responsible professional posts, and without criminal backgrounds. This group does not fit the social dropout image associated with terrorism. Discussion of the causes for terrorist involvement suggests the influence of liberal university environments at a time of personal insecurity in early adulthood. Tabular data and 9 references are given.