Purpuromycin (C₂₆H₁₈O₁₃) is a new antibiotic isolated from the culture broth of Actinoplanes ianthinogenes proposed as a new species on the basis of its morphological, cultural and physiological characteristics. The antibiotic, obtained as purple crystals, belongs to the naphthoquinone group of antibiotics and resulted to be related to rubromycins. The isolation and purification procedures and the chemico-physical properties of the product are reported. Purpuromycin is active in vitro against Gram-positive bacteria at 0.005-0.02μg/ml, at 1-20μg/ml on Gram-negative bacteria and at 0.2-0.5 μg/ml on fungi.