OBJECTIVE: To report an observation dealing with a possible side effect of a smoking cessation drug. DESIGN: A case report. STUDY PERSON: A 34-year old man who had been treated with slow-release bupropion for smoking cessation. OBSERVATION: After 5 days of treatment the patient suffered severe muscular pain and the diagnosis of rhabdomyolysis was confirmed. CONCLUSION: Rhabdomyolysis is a rare complication when treating with slow-release bupropion for smoking cessation.