Four fungi in the order Saprolegniales —Saprolegnia sp., Achlya ambisexualis, Leptolegnia eccentrica and Dictyuchus sterile– were tested for growth in synthetic media containing one of the following carbon sources: glucose, maltose, sucrose, alanine, proline, glutamate, leucine, arginine and phenylalanine. All of these compounds were effective substrates for one or more of the four fungi. The ability of Saprolegnia sp. to utilize other substrates was studied. Saprolegnia sp. can metabolize soluble starch, fructose, ornithine, aspartate, serine, and lysine but did not grow on galactose and eight additional amino acids.