New antibiotic, isohematinic acid, was found in the culture broth of an actinomycete strain SANK 61681, which was identified as a strain of Actinoplanes philippinesis. Fermentation of isohematinic acid was performed by conventional submerged culture in a 600-liter fermentor. Isolation of isohematinic acid was performed by adsorption of the antibiotic from the culture filtrate on a column of Diaion HP-20 followed by elution with aqueous acetone and extraction with ethyl acetate. Isohematinic acid was finally crystallized from hot methanol.