Individual curves for milk production of 428 cows affected by foot lesions were compared with control curves drawn from data of healthy lactating cows. First, differences were classified into patterns of milk loss, and their distribution was analyzed among the patterns with regard to breed, season, parity, stage of lactation, and milk production. Then, individual milk losses were estimated and analyzed according to the same factors. During early lactation, as during mid to late lactation, no marked modifications of the lactation curves occurred for about one-half of the cases. In 25% of the cases, milk production was affected for an expanded period (medians were 17 wk for early lactation and 12 wk for mid to late lactation). Corresponding median milk losses were 440 and 270 kg, respectively. Summer foot lesions were more severe than winter lesions, regardless of stage of lactation. Milk production at foot lesion onset was a determining factor of the amount and pattern of milk loss only for cases occurring during mid to late lactation.