Patients categorized according to tumor type were compared to a control non-tumor population. Comparison of relative T cell values among the groups showed no significant differences; however, when absolute numbers of T cells/mm3 were compared, all cancer patients, whether from treated or untreated groups, had significantly depressed T cell values. No significant differences were observed in the relative or absolute numbers of B cells. Comparison of the total lymphocyte response to PHA showed no significant differences among the various cancer groups; however, response in all cancer groups whether from treated or untreated patients, was depressed by comparison to the control group. Patients categorized according to the type of treatment received showed significant depression in the white blood count, lymphocyte count, relative and absolute T cell counts and the absolute B cell count in the postsurgery, postadjunctive therapy group. The pretherapy group also showed significant depression in the absolute number of T cells/mm3 when compared to the controls. Response to PHA correlated with the absolute T cells values.