Poly DL-lactic acid (PLA) is one of the biodegradable polymers. Bleomycin (BLM) incorporated into small cylinders of PLA blends was prepared as a new dosage (BLM-PLA). When BLM-PLA was preserved in saline, the dissolution rate of BLM from BLM-PLA was 49.2% after 7 days, 85.2% after 14 days and 99.7% after 21 days, respectively. BLM-PLA was implanted subcutaneously into the back of 36 rats. On days 3, 7, 14, 21, 28 and 35, the connective tissues near the implants, lymph node, lung, liver and kidney were removed and BLM activity was measured. The BLM concentration was maintained at a high level in the connective tissues until 14 days, and in the lymph node between 21 and 28 days. On the other hand, the BLM level was low in the lung, liver and kidney. Consequently, it was suggested that PLA is useful as a carrier for drug delivery system and that administration of BLM-PLA is an effective anti-cancer modality, especially in local chemotherapy.