The purpose of this investigation is to investigate HIV risk-related attitudes, beliefs, expectancies, behaviors, and histories of lifetime sexually transmitted diseases in the Millon Clinical Multiaxial Inventory III (MCMI-III) defined psychopathology cluster subgroups. Hierarchical agglomerative cluster analysis, using Ward's method, was employed that led to identification of high (n = 37), medium (n = 132), and low (n = 28) MCMI-III psychopathology cluster subgroups. Members of the low psychopathology subgroup demonstrated significantly higher levels of knowledge about HIV and AIDS and less anxiety about HIV infection than high and moderate psychopathology subgroups. The high psychopathology subgroup reported greater importance of approval of condom use by partners but less sexual self-efficacy than the moderate psychopathology subgroup. This high pathology group revealed less favorable condom attitudes than did the low psychopathology subgroup and a significantly higher percentage of unprotected vaginal sex acts in the past 6 months than did members of the other two subgroups. A comparatively low rate of lifetime syphilis was reported in the low psychopathology subgroup (all ps < .05). Results are discussed in the context of a growing literature indicating distinctive treatment needs among members of high psychopathology subgroups of drug treatment participants.