Genotype-by-environment (GxE) interactions for somatic cell score (SCS) and clinical mastitis (CM) were investigated in first lactation Normande cows. Milk and SCS herd-year effects estimated in the French national evaluation were used as environment descriptors of productivity level and health environment of the herds, respectively. Variance and covariance components were estimated using bivariate and reaction norm models. For SCS, heritability estimates ranged from 0.17 to 0.23 according to productivity level. Genetic correlations higher than 0.9 were estimated between groups, showing no GxE interaction for this trait with both models. For CM, the estimates of heritability ranged from to 0.01 to 0.07. Genetic correlations between and 0.3 and 0.99 were estimated across productivity levels and health environments, indicating GxE interactions for this trait.