The effect of subacute cold swimming stress on the immune system of albino rats was investigated. Subacute cold stressed animals showed an increase in total WBC count, eosinophils and basophils. Phagocytic index and avidity index were also increased indicating hyperactive phagocytic process. On the other hand NBT reduction and soluble immune complex levels decreased significantly in stressed animals. There were no significant changes in the weight of the lymphoid organs.