Three experiments were performed to assess the effects of expo­sure to acute heat stress (A.H.S.) (40°C) on the performance of Japa­nese quail chicks from one day old to six weeks of age. In all experi­ments, birds raised in heated batteries under continuous lighting, free feeding and water regimes. All experiments were started at one-day old and ended at six weeks of age. The results indicated that body weight (B.W.) was significantly decreased in 4 hr's-heat stressed (H.S.)group at 3, 4 and 5 wks of age. The highest B.W.was found in Ascorbic acids (A.A.) (500 mg) fed group. Feed intake decreased in H.S. 2 and 4 hr's and H.S.+fasting groups. Water consumption and mortality increased as HS period increased. These results suggest that AA addition to feed could ameliorate the negative effects of A.H.S. in Japanese quail.