Associations among diseases in dairy cows were studied on a two-consecutive-lactation basis by means of a longitudinal and prospective study carried out on 24 French herds, Associations between diseases of a given lactation and diseases of the previous lactation were adjusted for breed, parity, milk yield, season of calving, calving interval and type of housing, using multiple logistic regression models with random effects. Five of the 12 associations highlighted are recurrences (clinical mastitis within 5 days after calving, placental retention, lameness other than interdigital pododermatitis, reproductive disorders, milk fever). Otherwise, the study confirms the main role of placental retention in associations among diseases