This study compares the specificity and characteristics of two hard (Gruyère) cheese varieties manufactured at differents altitudes : 1) L`Etivaz cheese manufactured at L`Etivaz with two production sites (L`Etivaz 1 & L`Etivaz 2, 1300-2100 m) , 2) Gruyère cherese manufactured at Montbovon (1000 m) and at Grangeneuve (600 m). These four production sites were studied during summer 1995, from the beginning of June unti mid-September. Observations were carried out at each site : botanical composition of the pastures , chemical composition of the grass , chemical composition of milk, cream and cheese which was ripened over 8-9 months, as well as sensory and rheology properties of cheese. The grass composition was markedly different but the cheese production methods were similar excepted for milk heating (with open log fire producing some smoke in highland or in stream heated vats in lowland factories). All cheese loaves (n049) matured in the same ripening cellar under identical conditions. This study clearly highlights numerous differences of composition (heavy metals, fatty acids, triglycerides, volatile components including terpenoids, polyaromatic hydrocarbons and as well as flavour) between highland and lowland milk products