AbstractRats bearing (or not bearing) the Dunning R3327 MAT-LyLu prostatic adenocarcinoma were treated with Bacillus Calmette-Guerin (BCG) and evaluated for immune competence using functional and phenotypic markers. Tumor presence significantly depressed total T and helper T cell representation along with the helper/ suppressor T cell ratio. Functional immunity, measured by phytohemmagglutinin (PHA) induced blastogenesis, was also significantly depressed. When BCG was administered to non-tumor bearing animals, it had no effect upon T cell subset distributions but significantly reduced PHA induced blastogenesis. BCG similarly administered to tumor bearing animals did not alter the depressed helper/ suppressor T cell ratio found in tumor bearing rats, but did significantly elevate PHA induced blastogenesis. However, these elevated levels of functional immunity in BCG treated tumor-bearing rats remained significantly below normal. These data demonstrate a poor correlation between functional and phenotypic assessments of immune capabilty.