Amino acids can be utilized as a source of carbon and energy by many of the fungi in the class Oomycetes (Faro, 1971; Gleason, 1968; Gleason et al., 1970a, b). The number of amino acids which support the growth of a particular fungus as the single carbon source is quite variable among the Oomycetes studied. Furthermore, the rate of growth varies considerably with the amino acid provided. However, preliminary experiments with Leptomitus have shown that certain amino acids which cannot support growth individually will support growth when supplied as a mixture (Gleason, 1968). In their natural habitat Oomycetes come in contact with substrates rich in protein. These substrates must be attacked by extra-cellular proteases, releasing a mixture of amino acids which can be subsequently transported into the cell (Gleason et al., 1970b). Thus, these fungi are adapted to environmental conditions in which they are confronted with a mixture rather than a single amino acid. The uptake of individual amino acids from a mixture has not been measured in previous investigations on Oomycetes. This investigation was designed to measure the sequence and rate of uptake of 14 amino acids from a synthetic mixture by Saprolegnia sp. (47-15a). Each of 14 amino acids was added to a synthetic medium at a concentration of 0.3 g per liter: lysine, arginine, aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, methionine, isoleucine, leucine and phenylalanine. The total amount of the combined amino acids was 4.2 g per liter. A pH indicator (brom cresol purple), thiamin, and salts were added at concentrations given by Gleason (1968). The procedure for preparation of the medium, inoculation, and growth conditions are also described by Gleason (1968). During growth at 20 C on a rotary shaker, the pH was maintained close to 6.7 by aseptic addition of molar sulfuric acid. At intervals during growth 2-ml aliquots of the medium were removed from the culture vessel and