One of the most influential factors in science and medicine has been the development of placebo-controlled clinical trials. However, recruitment of patients for clinical trials is sometimes a major problem in clinical research. Successful patient recruitment may be enhanced with a clear understanding of the motivating factors that determine a patient's decision to enter a study. We have developed the Patients' Expectations, Attitudes and Knowledge (PEAK) Program consisting of questionnaires designed to study the factors motivating patients to enter a clinical trial, as well as capturing the experiences of research participants. A total of 247 female patients with dyspepsia (mean age: 43.9; range: 18.0-78.0 years) who entered either of two prospective double-blind, randomized, placebo-controlled multicenter trials in the USA completed PEAK Entry questionnaires during the first study visit. Based on their responses, the top three factors motivating patients to join the clinical trial were: interest in receiving investigational treatment with average score (AS) of 4.33 +/- 0.08 (M +/- SEM) on a 5-point scale, possibility of getting skilled professional care (AS = 4.07 +/- 0.09), and altruism expressed as an intention to help develop a new drug for the sake of other people (AS = 3.89 +/- 0.09). Age, ethnicity, and educational status significantly affected motivational factors of patients. These results indicate that recruitment can be enhanced by targeting these motivations in physician/patient communications, informed consent process and advertising for study participants.