This paper describes the time course of withdrawal and relapse in opioid-dependent volunteers (n = 8) who completed a gradual outpatient buprenorphine dose taper (28 days). Compliance with treatment was very high, as evidenced by clinic attendance (96-100%). Urinalysis showed that 6 of the 8 volunteers had relapsed to opiates by the end of the dose taper, even though reports of withdrawal were generally low. Relapse may have been triggered by a desire to re-experience the drug's positive subjective effects, craving, or low motivation to remain drug-free. A longer taper combined with an expanded range of treatments may improve prognosis.