The study investigated psychological morbidity and emotional stress symptoms, illness behaviour, coping mechanisms, social support and personality variables (locus of control) among HIV-infected subjects (n = 110) and patients with cancer (n = 136). Psychological morbidity was higher in HIV-infected (41%) than in cancer patients (22%). In comparison with the cancer group, the patients infected with HIV showed more emotional stress symptoms, maladaptive illness behaviour (hypochondriasis, dysphoria and irritability), ineffective coping mechanisms (hopelessness) and inadequate social support. In both the groups the level of global psychological stress was significantly correlated with poor coping mechanisms, maladaptive response to illness, external locus of control and weak social support, but not with medical variables. The implications of these findings are discussed. [ABSTRACT FROM PUBLISHER]