To develop a method for determining the acceptability and safety of ready-to-use therapeutic foods (RUTF) before clinical trialing. Acceptability was defined using a combination of three consumption, nine safety, and six preference criteria. These were used to compare a soy/maize/sorghum RUTF (SMS-RUTFh), designed for the rehabilitation of human immunodeficiency virus/tuberculosis (HIV/TB) wasted adults, with a peanut-butter/milk-powder paste (P-RUTF; brand: Plumpy'nut) designed for pediatric treatment.A cross-over, randomized, controlled trial was conducted in Kenya. Ten days of repeated measures of product intake by 41 HIV/TB patients,18 y old, body mass index (BMI) 18-24 kg · m(-2), 250 g were offered daily under direct observation as a replacement lunch meal. Consumption, comorbidity, and preferences were recorded.The study arms had similar age, sex, marital status, initial BMI, and middle upper-arm circumference. No carryover effect or serious adverse events were found. SMS-RUTFh energy intake was not statistically different from the control, when adjusted for BMI on day 1, and the presence of throat sores. General preference, taste, and sweetness scores were higher for SMS-RUTFh compared to the control (P0.05). Most consumption, safety, and preference criteria for SMS-RUTFh were satisfied except for the average number of days of nausea (0.16 versus 0.09 d) and vomiting (0.04 versus 0.02 d), which occurred with a higher frequency (P0.05).SMS-RUTFh appears to be acceptable and can be safely clinically trialed, if close monitoring of vomiting and nausea is included. The method reported here is a useful and feasible approach for testing the acceptability of ready-to-use foods in low income countries.