Low molecular weight physiologically active substance are useful at least as medicines or reagents for research. During our screening for new inhibitors, an actinomycetes culture produced inhibitor against histamine-release from rat mast cells. This inhibitor was isolated and named zincphyrin. The producing organism was isolated from a soil sample collected at Ooi-cho, Fukui Prefecture, Japan, and designated as AC8007 (FERM BP-10537). It was classified as Streptomyces from cultural characteristic or microscopic observation. Zincphyrin is a member of the porphyrin series with zinc elucidated by chemical analysis. Zincphyrin was primarily isolated as histamine-release inhibitor from mast cells. On extensive pharmacological studies, zincphyrin was found to have a potent photosensitizer activity. In this paper, we report the isolation, characterization and biological properties of zincphyrin.