Minority underrepresentation exists in medical research including cardiovascular clinical trials, but the hypothesis that this relates to distrust in medical researchers is unproven. Therefore, we examined whether African American persons differ from white persons in perceptions of the risks/benefits of trial participation and distrust toward medical researchers, and whether these factors influence willingness to participate (WTP) in a clinical drug trial. Participants were self-administered a survey regarding WTP in a cardiovascular drug trial given to 1440 randomly selected patients from 13 Maryland outpatient cardiology and general medicine clinics. Patients reported their WTP, rated their perceived chances of experiencing health benefit and harm, and rated their distrust toward researchers. Of eligible participants, 70% responded, and 717 individuals were included: 36% African American and 64% white. African American participants possessed lower WTP than white participants (27% vs. 39%, p = 0.001) and had higher mean distrust scores than whites (p < 0.0001). African American participants more frequently reported that doctors would less fully explain research participation to them (24% vs. 13%, p < 0.001), use them as guinea pigs without their consent (72% vs. 49%, p < 0.001), prescribe medication as a way of experimenting on people without their knowledge (35% vs. 16%, p < 0.001), and ask them to participate in research even if it could harm them (24% vs. 15%, p = 0.002). African American participants also more often believed they could less freely ask their doctor questions (8% vs. 2%, p < 0.001) and that doctors had previously experimented on them without their consent (58% vs. 25%, p < 0.001). African American participants expressed lesser WTP than white participants after controlling for racial differences in age, sex, socioeconomic status and cardiovascular disease risk profiles (multivariable odds ratio [OR], 0.57; 95% confidence interval [CI], 0.39-0.85). The impact of race was attenuated and nonsignificant after adjustment for potential mediating factors of racial differences in medical researcher distrust and perceived risk of harm (explanatory model OR, 0.84; 95% CI 0.54-1.30). In summary, African American participants expressed markedly greater concerns about experiencing harm from participation in clinical trials and distrust toward medical researchers than white participants. These factors, in turn, appear to explain much of the resistance among African American persons to participate in clinical trials compared to white persons.