BACKGROUND: The alleged efficacy of pharmaceutical industry self-regulation has been used to repudiate increased government oversight over promotional activity. European politicians and industry have cited Sweden as an excellent example of self-regulation based on an ethical code. This paper considers antidepressant advertising in Sweden to uncover the strengths and weaknesses of self-regulation. METHODOLOGY: We analyzed all antidepressant advertisements in the Swedish Medical Journal, 1994-2003. The regulation of these advertisements was analyzed using case reports from self-regulatory bodies. The authors independently reviewed this material to investigate: (1) extent of violative advertising; (2) pattern of code breaches; (3) rate at which the system reacted to violative advertising; (4) prevalence of and oversight over claims regarding antidepressant efficacy and disease causality, and (5) costs for manufactures associated with violative advertising. PRINCIPAL FINDINGS: Self-regulatory bodies identified numerous code breaches. Nonetheless, they failed to protect doctors from unreliable information on antidepressants, since as many as 247 of 722 (34%) advertisements breached the industry code. Self-regulatory bodies repeatedly failed to challenge inflated claims of antidepressant efficacy, lending evidence of lax oversight. On average, 15 weeks elapsed between printing and censure of a wrongful claim, and in 25% of cases 47 weeks or more elapsed. Industry paid roughly €108000 in fines for violative advertising, adding an estimated additional average cost of 11% to each purchased violative advertisement, or amounting to as little as 0.009% of total antidepressant sales of around €1.2 billion. CONCLUSIONS: Lax oversight, combined with lags in the system and low fines for violations, may explain the Swedish system's failure to pressure companies into providing reliable antidepressants information. If these shortcomings prove to be consistent across self-regulatory settings, and if appropriate measures are not taken to amend shortcomings, many countries may want to reconsider the current balance between self-regulation, and legislative control with government oversight.