IN the Research Items in NATURE of April 29, an account is given of the production of antibiotics by Aspergillus fumigatus. To supplement this annotation we submit this short account of our own work with the mould Aspergillus fumigatus mut. helvola Yuill. An earlier publication1 has described the isolation of helvolic acid from 2-3-week cultures of this mould grown at 25° C. on a medium containing mineral salts and 4 per cent of glucose.