Mycophenolic acid (MA) inhibits the growth of some pathogenic fungi such as Candida albicans, Cryptococcus neoformans and several species of Trichophyton at low concentrations in vitro. The antibiotic is more effectvie against fungi at slightly acidic pH than neutral pH. When administered to mice through the intraperitoneal, intramuscular and oral routes MA excreted to a few per cent in the urine. However, at no time was active MA detectable in the blood of mice. MA is effective against experimental trichophytosis of the guinea pigs, without noticeable skin irritation or inflammation. © 1969, JAPAN ANTIBIOTICS RESEARCH ASSOCIATION. All rights reserved.