In recent years, drugs including flunitrazepam, gamma-hydroxybutyrate, ketamine, and ethanol, have become popularly associated with drug-facilitated sexual assault. Other drugs are also candidates as factors in "drug facilitated sexual assault" (DFSA). The true extent of DFSA is not known, and is difficult to estimate. We recruited sexual assault complainants at four clinics in different parts of the U.S. to anonymously provide urine and hair specimens, and to answer questions about suspected drugging, drug use, and the sexual assault incident. Urine and hair specimens were tested for 45 drugs, including ethanol, and those pharmacologically capable of inducing sedation, amnesia, or impairment of judgment. Analytical test results were used to estimate the proportion of subjects, and the proportion of all complainants to the clinic in the same time period, who were victims of DFSA. Overall, cases of 43% of 144 subjects, and 7% of 859 complainants, were characterized as DFSA. Subjects underreported their use of drugs. The role of toxicological results and history in characterizing DFSA cases is discussed.