Two times epidemiological investigation were made to acquire the rules and characters of the incidence and morbidity of rickets and the epidemical factors of rickets in spring and autumn 1987 in Dali county. The result showed that there were 930 parents with rickets in 1988 children aged 0～3 years. the morbidity rate was 46.8% and the incidence rate was 69.6% in the infants aged 0～1 years. The morbidity rate showd a tendency to decrease according as the age in creased. The differences of the morbidity rate among age brackets were very significant (P