To evaluate the effects of a mixture of sulfachloropyridazine sodium (100 ppm) + trimethoprim (20 ppm) in promoting growth and improving feed efficiency of starting pigs, a total of 80 weaning three-way crossbred (Yorkshire × Landrace × Duroc) pigs weighing an average of approximately 10㎏ was used for a period of 50 days. Animals were divided into 8 pens of 10 pigs each. Each pen was assigned to one of 2 treatments with 4 replications (2 pens of males and 2 pens of females). Animals were fed a pig starter diet either with or without supplementation of sulfachloropyridazine sodium + trimethoprim (S + T). Pigs fed the diet containing S+T mixture gained significantly (P $lt; 0.01) more weight than nonmedicated control pigs. Medicated animals consumed numerically more feed than nonmedicated animals and feed efficiency was improved by feeding S+T mixture, although differences in feed intake and feed efficiency were not statistically significant.