Motivational enhancement therapy (MET) is a brief therapy shown to be effective for problem drinkers. Because the response to MET for other addictive disorders is mixed, we assessed the utility of increasing the number of sessions in subjects with methamphetamine (MA) dependence. One therapist was trained in a nine-session manual of MET, which was tested over eight weeks in 30 MA-dependent outpatients. Adherence to the manual was assessed by two raters, who reviewed a random sample of 15 audiotaped therapy sessions. Interventions were rated on a seven-point Likert scale for frequency/extensiveness (1 = not at all to 7 = extensively) and skill level (1 = unacceptable to 7 = high level of mastery). Ratings of adherence were moderate for frequency/extensiveness (4.2 +/- 2.2 and 4.3 +/- 1.8; Mean +/- SD) and high for skill level (5.4 +/- 0.6 and 5.2 +/- 0.4). Subjects attended 7.0 +/- 2.5 (78%) of nine sessions. Self-reported days of methamphetamine use decreased from 841/1793 (47%) of the 60 days prior to study entry to 448/1458 (31%) during the study (p = 0.011). MA-positive urine samples decreased from 76/118 (64%) during screening to 93/210 (44%) during treatment (p = 0.015). The MET manual was readily learned, and subjects attended a high proportion of therapy sessions with marked reductions in methamphetamine use.