The effect of treatment with bacterial preparations on blood flow in normal and malignant tissues was investigated, clinically and experimentally. The time course of the local effect of the preparations was recorded by Laser Doppler Velocimetry (LDV) via a probe on the surface of normal and malignant tissues directly over the injection site. Experimentally, no definite enhancement of blood flow with OK-432, a streptococcal preparation, was observed in nude mice. Clinically, intradermal administration of OK-432 or tuberculin (PPD) resulted in an approximate 11-or 4-fold increase in blood flow, respectively. The injection of OK-432 into malignant tissues, such as dermal cancer and breast cancer with direct extension to the skin, resulted in an approximate 3.5-fold increase. The results suggested that bacterial preparations can act as an adjuvant to enhance drug delivery to tumor tissue in cancer chemotherapy, and that the enhancement of blood supply is induced by immune response.