The possible presence of toxic metabolites in the culture extracts of 24Ascochyta strains, grown on autoclaved wheat, was ascertained by the use of the biological assay on brine shrimps (Artemia salina). Only in the culture extract ofA lathyri, that showed a very high toxicity, the presence of cytochalasins A and B was revealed by tlc,(1)H nmr and fab-mass spectra.SinceA heteromorpha, previously described as the firstAscochyta species to produce cytochalasins, has been reclassified asPhoma exigua varheteromorpha, this is therefore the first report on the cytochalasin production by a trueAscochyta species.