Improving communication about cancer clinical trials may help increase patients' understanding of medical research and their interest in participating. It is unfortunate that there is little empirical research to provide guidance on how to adapt clinical trial messages to maximize cultural sensitivity. This study examines (a) how medically underserved women conceptualize clinical trials by examining the language they use to describe them and (b) how this audience interprets metaphorical language used to explain randomization in the context of Phase III cancer clinical trials. The author conducted in-depth interviews and focus groups with 41 rural, low-income older women who either had been diagnosed with cancer or were caregivers for a person with cancer. The most commonly used lay metaphors for clinical trials had strong negative connotations and included treatment by trial and error, patients are guinea pigs, and treatment of last resort. Participants also expressed strong, unfavorable responses to conventional metaphors that equate randomization with the roll of a die or use other gambling language. Low-literacy definition approaches were unexpectedly problematic, suggesting the potential effectiveness of culturally grounded metaphors for communicating about clinical trials. Ethical implications of these findings for cancer communication are discussed.