The effect of multiple stresses on chick performance is of interest. In this work the effect of ammonia and NDV stresses on broiler performance and the role of ascorbic acid in the alleviation of these effects were studied. The results indicated that: 1. Exposure of broilers to ammonia stress early in life affected organ's weight in various ways decreased than the control then increased with age and ascorbic acid supplementation. 2. NDV challenge resulted in more organ's weight as a single stress than with ammonia and ascorbic acid supplement. 3. Ascorbic acid retarded the stressfulness effect on bird's internal organs. 4. Haematological changes were obvious in single stress or double without ascorbic acid treatment. Ammonia increased HetcrophilAymphocyte (H/L) ratio in early life then declined with age and ascorbic acid Supplement. 5. Exposure of birds to each stress decreased food/gain ratio but the supplementation with ascorbic acid improved this ratio and mortality rate. 6. The ammonia as a stress factor affected the liver and kidneys with necrotic changes, and the immune organs (thymus, spleen and bursa of Fabricius) with lymphocytic depletion. Such lestons appeared more extended and severe on using NDV instead of ammonia. Ascorbic acid treated ammonia alone or with NDV stress got more improvemnt in the degree of the previously mentioned lesions with hyperplasia of reticular cells in the lymphoid organs.