Fourteen out of 26 patients with invasive bladder cancer were randomly assigned to receive weekly subcutaneous injections of Corynebacterium parvum (CP) in addition to standard treatment. Peripheral blood T lymphocyte percentage, K cell activity, mitogen responsiveness, and monocyte and polymorph leucotaxis were measured at intervals over a period of 1 to 2 years. The only consistent difference between the CP-treatment patients and the controls was a slightly higher level of K cell activity in the former, who, however, fared rather worse than the controls in terms of survival.