The composition of fatty acids (approx. 70 acids) in 44 summer milk samples from three geographical sites was determined using high-resolution gas chromatography. We observed large differences between Lowlands (600-650 m), Mountains (900-1210 m) and Highlands (1275-2120 m) which are analogous to those observed between winter and summer fats. The largest relative increases as a function of the altitude of these three sites were those of the concentration of conjugated linoleic acids (0.87, 1.61 and 2.36 g 100 g(-1)), especially of the cis (c) 9 trans (t) 11 isomer (0.81, 1.50 and 2.18 g 100 g(-1)), and the fatty acids C18:1 t10 + t11 (2.11, 3.66 and 5.10 g 100 g(-1)). There were significant differences in the concentration of fatty acids between the three geographical sites. Some fatty acids could also be interesting potential indicators for the origin of cream and also of the Protected Designated Origine ``mountain`` cheeses. (C) 2002 Elsevier Science Ltd. All rights reserved