Mephedrone was the least known of the four drugs, with only 27 percent of the respondents reporting knowledge of the drug. Less than 1 percent had used the drug in the previous 12 months. Four percent of the detainees knew of someone who was dealing mephedrone at the time of the interview. Detainees in East Perth were the most likely to report knowledge of mephedrone. GHB was familiar to 53 percent of the detainees and had been used in the 12 months prior to the interview by 3 percent of the detainees; 8 percent of detainees had been offered GHB, and 6 percent knew of a dealer selling GHB. Ketamine was known to 43 percent of the detainees, and it had been used by 3 percent in the last 12 months. The prevalence of ketamine use among detainees was the same as with GHB (3 percent); knowledge of a current ketamine dealer was 4 percent. Rohypnol was the most widely known of the four drug types (59 percent); however, use of the drug by detainees in the 12 months prior to the interviews was lower than for GHB or ketamine (1 percent). Although the findings indicate a relatively low level of use of the four drugs, there remains a need for ongoing assessment in order to identify changing trends and patterns of use that must be addressed. 4 tables and 13 references