[en] Experiments described here were carried out to assess the influence of host immunosuppression on Bacillus Calmette Guerin (BCG) contact suppression of a syngenetically transplanted 3-methylcholanthrene-induced rat sarcoma, Mc7, by 450 rad whole body γ radiation at 7 rad/min. The results suggest that augmented systemic responses to tumour-associated rejection antigens are not essential for BCG contact suppression but it is stated that the nature of the responses involved have yet to be elucidated. (U.K.)