In an ongoing study intended to develop an interview method for assessing drug abuse and dependence, 52 of 173 (30%) adolescents reported using ecstasy 5 or more times in their lives (those reporting less than 5 uses not reported). The sample was recruited from advertisements posted in high schools and college dorms, through snowball sampling, and from an inpatient substance abuse treatment facility. 94% (approx. 49) reported recent ecstasy use, and use of other drugs (especially alcohol, cannabis, stimulants and hallucinogens) was often reported. "Withdrawal" effects reported after ecstasy use included feeling tired or sleepy and change of appetite, and 59% (approx. 31) reported some withdrawal symptoms. Using ecstasy despite knowledge of [negative] physical or psychological effects was the most commonly endorsed dependence criterion , endorsed by 63% (approx. 33). 45% (approx. 23) reported hazardous use of ecstasy (when driving, before/resulting in unprotected sex), a criterion for abuse. The authors then classified 43% (approx. 22) of their sample as dependent on ecstasy and 34% (approx. 18) as meeting criteria for abuse of ecstasy, while 23% (approx. 12) were not classified as either, only 18% (approx. 9) reported ecstasy cravings. While this study found higher rates of dependence and abuse than in was reported in another study (Schuster et al. 1998), the sample is relatively small (compared to that of Schuster) and respondents were selected on the basis of regular ecstasy use, and thus cannot be considered representative of all ecstasy users. It seems inappropriate to refer to sub-acute effects reported after ecstasy use as indicators of "withdrawal," as previous retrospective studies (Solowij and Hall 1992; Liester et al. 1991) and laboratory studies with MDMA (Vollenweider et al. 1998) indicate that these effects appear after a single use and are not associated with chronic use or dependence.