Although federal initiatives have mandated broader inclusion of minorities in clinical research on diseases that have disparities in health by race and ethnicity, it is not clear whether these initiatives have affected reporting of trial results. The objective of this study was to examine the reporting of race/ethnicity in clinical trials reports in areas of known disparities in health (i.e., diabetes, cardiovascular disease, HIV/AIDS, and cancer) and to determine what factors were associated with reporting of race/ethnicity in results. We performed a Medline search covering the period January 1989 to Oct 2000 to identify clinical trials of diabetes, cardiovascular disease, HIV/AIDS, and cancer published in the Annals of Internal Medicine, JAMA, and New England Journal of Medicine. The main outcome measure was the reporting of participation and of results by race/ethnicity of trial participants. Of 253 eligible trials, 40% (n=102) were non race-focused yet did not report race, while 2% (n=4) were non gender-focused and did not report gender. Forty-six percent of trials that reported the race/ethnicity of the sample reported only one or two racial/ethnic categories, and in 43% of these trials the total number of individuals reported in each race/ethnicity category did not equal the total reported sample size. Analysis of results by race/ethnicity was reported in only two trials, and by gender in only three trials. In diseases with known racial and ethnic disparities, many clinical trials do not report the race/ethnicity of the study participants, and almost none report analyses by race/ethnicity. Although federal initiatives mandate inclusion of minority groups in research, that inclusion has not translated to reporting of results that might guide therapeutic decisions.