Intratumoral injections of 10 mg cells walls from Propionibacterium granulosum strain KP-45 (PG) were applied in 14 patients with advanced, metastatic stomach (five cases) and colorectal (nine cases) adenocarcinoma. Each patient had his own "twin" control. All patients received no other anticancer treatment, except analgetics and/or palliative surgery. Treatment with PG resulted in partial regression of tumors accompanied by improvement of the clinical state of these patients as well as the reappearance of normal values in blood count biochemical parameters. In each pair of twin cases, survival of the PG-treated patient was longer than the untreated control. The mean survival of PG-treated patients was 23.5 months (4 of 14 patients being still alive after 2.5 years follow-up), while all control patients died with a mean survival period of 6.4 months. The difference between these two patient groups of about 17 months is significant (p greater than 0.01).