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Observations on 7416 Canadian Holstein cows were examined to estimate genetic parameters for the most common diseases of dairy cows. Mastitis, ovarian cyst, ketosis, milk fever, abomasal displacement, and culling that is due to reproductive failure or leg problems were analyzed as binomial traits, assuming an underlying threshold model that included fixed and random effects. Sire and residual components of variance were estimated by REML to provide heritability estimates from paternal halfsibs. A multiple-trait mixed model was also used to estimate genetic and environmental correlations between production and disease traits. Heritabilities of disease traits were relatively low and ranged from 0 to .15, except for displaced abomasum (h²=.28). Evidence of genetic antagonism existed between incidence of mastitis and milk production. Incidence of milk fever was genetically associated with cows of lower …