In our screening program for phospholipase C (PLC) inhibitors from microbial origin, we isolated a novel PLC inhibitor, Ro 09-1450 from the culture broth of Penicillium vinaceum Gilman & Abbott NR6815. Ro 09-1450 was purified by EtOAc extraction, precipitation and recrystallization from EtOAc. The molecular formula of Ro 09-1450 was determined to be C_ H_ O_ by elemental analysis, NMR and mass spectrometry. The structure of Ro 09-1450 was determined to be 1 by 2D-NMR spectroscopy (INADEQUATE, HMBC and COLOC) and chemical derivatization. Ro 09-1450 showed selective inhibitory activity against PLCs from rat brain, murine colon 26 adenocarcinoma and murine fibroblastsNTH3T3 with IC_ 's of 5.4μM, 9.3μM and 44μM respectively.