The [ ll]cytochalasin deacetylcytochalasin H (7,18,21-trihydroxy-16,18-dimethyl-l0-phenyl-[ ll]cytochalasa-6(12),tram-13,tram-19-trien-l-one) was isolated and identified from culture extracts of Phomopsis sp. by use of spectroanalytical techniques. Biological data presented an LDM in chickens of a single oral dose at 37.5 mg/kg and plant growth inhibitory activity down to M in wheat coleoptiles.