[en] This study was carried out at the experimental animal house and laboratory belonging to poultry physiology unit, Biological Application Department, Atomic Energy Authority, Egypt from November to December(2008). The aim of this work was to investigate the effects of supplementing broiler diets with active dried yeast; Saccharomyces cerevisiae (Sc), vitamin C (Vit.C) or their combination to alleviate the deleterious effect of ochratoxin A (OA) on productive performance, weights, functional and histological profile of internal organ and physiological and immunological parameters. A total number of 368 sexed male Ross broiler chicks were used in this study. The chicks were randomly distributed according to diet supplementation into eight groups (46 chicks each) from 1 day old to 5 weeks of age. The results obtained showed that presence OA at 200 ppb in broiler diets caused significant decrease in body weight, feed consumption and worse feed conversion ratio, hemoglobin, packed cell volume of blood, red and white blood cell counts, blood proteins, thyroid hormones, immune response and weights of thymus and bursa and alteration in histological picture of kidney, liver and bursa. At the same time, a significant increase in relative weights of kidney, liver, gizzard, proventriculus, AST, ALT enzymes, uric acid, creatinine in addition to high mortality percentage. Addition Sc either alone or in combination with vit.C to OA- fed groups alleviated the toxic effects of OA on productive performance, immunological, hematological, biochemical and histological parameters. On the other hand, the addition of vit.C to OA- contaminated broiler diet did not prevent the negative effects of OA observed in chicks, except for some measurements as body weight, mortality percentage and blood proteins, although less extent was shown compared to the Sc or Sc + vit.C supplementation.