This study examined, in health care attenders, the effect of different sociodemographic variables and physical illness on the probability of suffering from mental disorders. In health centres, the prevalence of mental disorders was 19.3% (12.4% for males and 23.8% for females). Logistic modelling was used to investigate the joint effect on psychiatric morbidity of 6 sociodemographic variables and physical illness. It was found that sex, age, and physical illness exerted independent but not interactive effects on the probability of psychiatric morbidity.