Fifteen strains of Trichoderma belonging to 12 different species for potential use in biological control were examined for their ability to produce polypeptide antiobitics (peptaibols). Gas chromatography was used to detect the hydrolysis products of peptaibols after esterification with n-propanol and derivatisation with heptafluorobutyric anhydride. In particular, amino acids (alpha-aminoisobutyric acid, and isovalin) and amino alcohols (phenylalaninol, leucinol, and valinol) were used as markers for the detection of different peptaibols. alpha-Aminoisobutyric acid, an amino acid characterising all peptaibols, was detected in all cultures examined, indicating that the production of peptaibols is a common feature of the various Trichoderma species. Different amino acid/amino alcohol combinations suggested specific peptaibol production. On this basis, the peptaibol paracelsin was confirmed by HPTLC in 11 out of 15 Trichoderma strains cultures. Valinol was not found in any culture extract, indicating the lack of trichotoxins production. Culture extracts of the 6 tested Trichoderma strains were extremely toxic to Artemia salina larvae; for 5 of them this toxicity could be attributed to paracelsin (calculated LD50 = 2.2 microM).