The freezing point of bovine milk is known to vary between narrow limits. However, some variation is possible, because of the osmotic relationship between blood and milk. The extent of variation in freezing points of cow's milk was studied. For one year, freezing points were determined in individual milk samples from a high producing herd. Differences (P<0.05) were found between evening and morning milk yield and freezing points. A ‘lactation curve’ for freezing points was fitted and showed some similarity with milk yield curves. Stage of lactation explained part of the variation of freezing points of cow's milk.