Introduction: There is little empirical evidence on voluntariness of participation in clinical trials due to absence of acceptable measures and universally accepted conceptual frameworks of voluntariness. Methods: A cross-sectional study was conducted in Zimbabwe to examine participants’ motivations, levels of voluntariness and perceptions about the effect of offers, pressures and threats on decision making. One hundred participants were recruited from an ongoing diagnostic trial. Questionnaires adapted from published research, the Perceived Coercion Scale and Voluntariness Ladder were used for data collection. Results: The need to access diagnostic services and treatment for tuberculosis was the main motivation for enrolment in the trial. Participants were not coerced to particpate in the trial but were offered bus fare. The offer had no effect on their decision to enroll in the trial. Conclusion: Immediate health benefits have a key impact on participants’ decisions to enrol in a clinical trial of a diagnostic technique. A comprehensive conceptual framework together with validated tools for assessing voluntariness in African contexts should be developed. / Thesis (M.Soc.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.