The individual and combined effects of T-2 toxin (0.5 ppm) and endosulfan (20 ppm) were studied in broiler chicken by feeding the toxins from 0 to 4 weeks of age. There was significant (P<0.05) reduction in the body weight gain in the T-2 toxin fed groups compared to the control. Hyperproteinaemia, increased GGT, decreased creatinine, increased uric acid, hyponatraemia, hypertriglyceridaemia, decreased LDL and increased VLDL were observed in the endosulfan fed groups. Increased ALT and hyponatraemia were observed in the T-2 toxin fed groups. Hypoglobulinaemia, increased amylase, BUN, uric acid and hyponatraemia were observed in the T-2 toxin+endosulfan fed birds. Significant (P<0.05) increase in the GST and decrease in the catalase were observed in the endosulfan fed groups. The T-2 toxin fed birds showed significant (P<0.05) decrease in the catalase. Significant (P<0.05) increase in the liver lipid peroxidation and decrease in the catalase were observed in the T-2 toxin+endosulfan fed groups. Significant (P<0.05) increase in the weight of liver in endosulfan fed birds and spleen in the T-2 toxin and T-2 toxin+endoslfan fed birds were found. Grossly, liver was pale and enlarged in the endosulfan fed birds. Degenerative hepatocytes, microgranuloma, periductular mononuclear cell infiltration, venous dilatation in the liver, degenerative changes in the tubular epithelial cells and focal mononuclear cell infiltrations in the kidneys, hyperplasia, hyperkeratosis and parakeratosis of crop mucosa, proventriculitis, ventriculitis, fusion and stunting of duodenal villi, lymphoid depletion in the bursa of Fabricius and caecal tonsils and mild lymphoid depletion and reticulum cell hyperplasia in the spleen were observed in the toxin fed birds. The serum antibody titre to NDV and the stimulation index of splenocytes were not altered significantly in the toxin treated birds when compared to the control. For NDV-toxins interaction studies, 48 day-old broiler chicks were randomly allotted into two groups of four replicates and fed with T-2 toxin (0.5 ppm) and endosulfan (20 ppm). One group was vaccinated with NDV-F on day 6. The birds were challenged with NDV on 21st day. The birds that succumbed to NDV infection exhibited dullness, depression, loss of appetite, ruffled feathers and greenish watery diarrohea, gasping, closure of eyelids, unilateral or bilateral paralysis of legs and wings. Mortality was 50 per cent in the T-2 toxin fed group and 33.33 per cent in the endosulfan fed groups. Severity of lesions in the lymphoid organs depended on the survivability of the challenged birds. The toxins induced apoptosis and necrosis in the thymocytes and splenocytes at 48 h. T-2 toxin (1.0 ppm) and endosulfan (50 ppm) caused significant (P<0.05) increase in the percentage of CD4 and CD8 T-cells in the thymus. To conclude, the study revealed that T-2 toxin and endosulfan affected the performance and health of birds and the effects were not additive or synergistic.