A survey of 70 insightful clinically stable out-patients with functional psychotic disorders and 70 accompanying relatives was carried out. They were interviewed about their beliefs concerning the cause of the illness, and their awareness of other possible aetiological factors. Relevant sociodemographic and clinical information were also elicited. Twelve (17.1%) patients and relatives, respectively, gave "medical" causal explanations; 16 (22.9%) patients and 13 (18.6%) relatives gave "psychosocial" causal explanations; 27 (38.6%) patients and 38 (54.3%) relatives were "uncertain" about the cause of their/relatives' illness (X2 = 5.08; df = 3: P = 0.16). Relatives reported a greater relevance of "heredity" (X2 = 11.58; P = 0.0006) and "supernatural" factors (X2 = 4.72: P = 0.029) as other possible causal factors, than patients. Patients with previous psychiatric hospitalisation reported higher prevalence of "psychosocial" and "supernatural" causal beliefs than those without (X2 = 9.15; P = 0.027). Also, patients with "medical" causal belief reported better treatment compliance than those with other beliefs (P = 0.031). Among relatives, "psychosocial" causal belief in comparison with other beliefs was associated with a longer duration of treatment in the hospital (h = 8.29; P = 0.04). For patients, knowledge about possible causal role of "heredity was significantly more prevalent among male than female patients (X2 = 6.55; P = 0.01) and admission of possible "supernatural" causation was associated with education below the secondary level (X2 = 6.68; P = 0.008). For relatives, knowledge about possible causal role of brain dysfunction was associated with longer duration of treatment (u = 3.93; P = 0.047), and knowledge of possible causal role of "psychosocial" stress was associated with urban place of residence rather than rural (X2 = 10.52; P = 0.0012). For both patients and relatives, the most acceptable aetiological proposition was the "supernatural" while the least was "psychosocial". Findings revealed, among others, the widespread belief in "supernatural" causation of mental illness in patients/relatives. Some identified significant findings may be relevant in mental health education programme development.