Objectives. As in many settings, patients in community health centers in Ecuador do not complete previsit forms or receive assistance to identify questions and concerns they would like to address in brief clinic visits with physicians. We examined the comparative effectiveness of providing (1) a previsit form to complete; (2) a previsit form along with assistance in completing the form; and (3) usual care. Methods. Parallel, three-arm randomized controlled trial in two health centers serving indigent to low-income communities in Quito, Ecuador, among 199 adult patients who took medications for at least one chronic condition. Outcome measures were self-reported satisfaction with the visit, confidence in asking questions, and extent to which patients' objectives were met. Results. Patients who received assistance in completing a previsit form were more than twice as likely as participants in usual care to report achieving everything they wanted during their visit (AOR 2.2, P = 0.039). There were no differences in any outcomes between the groups who received the previsit form with no assistance and usual care. Conclusions. For high-quality patient-centered primary care, it is important to develop and test innovative and scalable interventions for patients and physicians to make the best use of limited clinic time.