This study investigated the extent of hallucinogenic mushroom use among 1507 college students and compared mushroom users to nonusers. The subjects, who completed an anonymous questionnaire, were students from California State University, Northridge, and the University of California, Los Angeles. The major finding was that among the respondents who reported use of hallucinogenic drugs (17%), over 85 percent had used hallucinogenic (psilocybin) mushrooms and over half had used mushrooms but no other hallucinogens. The data suggest a high level of experimental use compared to other hallucinogens. Survey research into hallucinogenic mushroom use should be extended, and mushroom use should be distinguished from use of other hallucinogens.