To determine the bioavailability of industrially heat-treated milk proteins, male Wistar rats were given [15N]-labeled meals containing either nonheatedsmicellar casein (CAS), milk soluble protein isolate (MSPI), and microfiltered milk (MF)sor heated productss“high temperature short time” pasteurized (HTST), “higher temperature, shorter time” pasteurized (HHST), ultrahigh temperature-treated (UHT), and spray-dried (SPRAY) milks. The postprandial distribution of dietary nitrogen was measured in the splanchnic area and urea. Digestibility was around 96% except for SPRAY (94%) and MSPI (98%). Ingested nitrogen recovered in the splanchnic bed was 19.3% for SPRAY, 16.7% for MF, and around 14-15% for other products. Deamination of dietary nitrogen reached 21.2, 20.6, and 18.2% of ingested nitrogen for MSPI, SPRAY, and CAS, respectively, and around 14-16% for other products. In our model, only spray drying led to a significant increase of splanchnic extraction. Moreover, the biological value of purified protein fractions appeared to be lower than that seen in products containing total milk protein.