SUMMARYTwo isolates ofF. roseumwere grown in a chemically defined liquid medium containing MgSO4, microelements, and a carbon and nitrogen source. The relation of time to mycelium formation in shaken and stationary cultures was studied. Shaking did not significantly alter the rate of growth nor the maximum amount of mycelium produced. Maximum mycelium had formed by the sixth or ninth day with glucose and asparagin. The two isolates differed in their response to the various carbon sources studied. The best carbon sources for both isolates were xylose, galactose, maltose, sucrose, raffinose, and starch. Glucose and cellobiose supported only moderate growth. Lactose, cellulose, alcohols and organic acids (acetic, citric, fumaric, lactic, malic, succinic, tartaric) were relatively poor sources of carbon, although growth occurred in all. The two isolates utilized a variety of nitrate, ammonium and organic nitrogenous compounds with glucose as the carbon source; however, they differed in their response to specific compounds. Isolate No. 1 consistently produced more mycelium than isolate No. 2. Generally, organic nitrogen was the best source, ammonium compounds next best, and nitrates the poorest. The pH values of the residual liquid media was determined at the end of all experiments and no inhibitory pH levels developed.