Effects of different term of exposure to hot environments on metabolic response was studied in four adult not-pregnant and not-lactating Sardinian ewes housed in a climatic chamber. The trial lasted 83 days. Fifteen days were spent under thermal comfort (TC) conditions (temperature-humidity index (THI)=65.0±4.0), 48 days were spent under hot environment (HE) conditions (THI=82.0±3.5) and the last 18 days were spent under TC (THI=65.0±1.0).