To compare findings from two consecutive clinical trials of auricular acupuncture for cocaine addiction conducted at the same site in order to explore consistency of treatment effects. One hundred and sixty-five (165) cocaine-dependent, methadone-maintained patients (study 1, n = 82; study 2, n = 83). Subjects in both studies were randomly assigned to auricular acupuncture, a needle insertion control condition, or a no-needle relaxation control. Treatment sessions were offered five times weekly for 8 weeks. The two studies were equivalent in design, except that unlike study 1, study 2 offered subject payments for attendance and did not include weekly group counseling. Cocaine use assessed by three times weekly urine screens constituted the primary outcome. Secondary measures included retention in treatment, treatment attendance, treatment credibility, therapeutic alliance, and acute effects of treatments. Intent-to-treat analysis showed that patients assigned to acupuncture in study 1, but not in study 2, were significantly more likely to provide cocaine-negative urine samples relative to the two control conditions. The positive effect for acupuncture found in study 1 was not found in study 2. Even though the two studies were similar, reasons for this inconsistency cannot be determined definitively, but may be because of differences in psychosocial context and payment contingencies between the two studies, or the lack of effectiveness of acupuncture in this application. The need to critically consider the influence of treatment context and other potential moderating variables on outcome in order to draw conclusions regarding treatment effectiveness is discussed.