STUDY PARTICIPANT COMPENSATION IS OF increasing concern, yet few investigations have explored it; none have examined whether published journal articles report it. Medline searches for articles in six areas-HIV, substance abuse (heroin and cocaine), depression, essential hypertension, and cardiac surgery-reveal very low mention of payment (0-32.1%). Of 207 articles, only 13.5% mentioned financial compensation in any way, and only 11.1% listed amounts. Of the 207 studies, 92 involved more than minimal risk interventions, but were not more likely to mention compensation. Studies that included substance users were significantly more likely than others to mention payment (p < .001). These overall low rates are concerning as they can hamper evaluation of ethical issues, and impact study replicability. Publication requirements should consider discussion of compensation.