Dietary therapy plays an important role in the management of most gastrointestinal disorders. This study was designed to test the efficacy of a new therapeutic diet for cats with diarrhea, compared to the top selling brand. Sixteen adult cats with chronic diarrhea were grouped and assigned to diet X (Hill's Prescription Diet i/d Feline) or diet Y (Purina Veterinary Diets EN Gastroenteric Feline Formula). Following baseline evaluations, cats were fed their assigned test diet for 4 weeks. Fecal scores (FS; 7=very watery; 1=extremely dry and firm) were recorded daily during the last week on each diet. Each cat was then switched to the alternate test diet and the procedure was repeated. Fifteen cats completed the study. Both therapeutic diets resulted in a significant improvement in average FS and diet Y also resulted in significantly better results compared with diet X. Average FS improved at least one unit in 40% of the cats while fed diet X and in 67% of the cats while fed diet Y, resulting in normal stools (average FS≤3) in 13.3% of cats fed diet X and 46.7% of cats fed diet Y. This study confirms the value of dietary change in the management of chronic diarrhea in cats.