The objective of this study was to validate three different models for predicting milk urea nitrogen. 4.749 observations from 855 cows were used. Milk production, body weight, days in milk and lactation number were recorded at milk sampling. Milk was sampled monthly for milk composition analysis. To evaluate the models, they were tested for accuracy, precision and robustness. Model 2 (Kauffman and St-Pierre, 2001) despite being more accurate, was less precise than model 3 (Kauffman and St-Pierre, 2001), while model 1 (Jonker et al., 1998) was the least accurate and the least precise. Models were not robust.