The authors made a field-survey of mental morbidity in all the tribal and caste groups residing in a cluster of villages in West Bengal, India, and found that, in each group, higher socio-economic classes had higher rates of mental morbidity. Different groups having a similar cultural pattern showed no significant difference in their rates of morbidity. Groups having different cultural patterns differed significantly in their rates of morbidity. In the tribal groups some neurotic disorders were absent.