We previously have shown that ingested beef protein is just as potent as glucose in stimulating a rise in insulin concentration in type II diabetic patients. A synergistic effect was seen when given with glucose. Therefore, we considered it important to determine if other common dietary proteins also strongly stimulate an increase in insulin concentration when given with glucose. Seventeen type II (non-insulin-dependent) untreated diabetic subjects were given single breakfast meals consisting of 50 g glucose, or 50 g glucose plus 25 g protein in the form of lean beef, turkey, gelatin, egg white, cottage cheese, fish, or soy. The peripheral plasma concentrations of glucose, insulin, glucagon, alpha amino nitrogen, urea nitrogen, free fatty acids, and triglycerides were measured. Following ingestion of the meals containing protein, the plasma insulin concentration was increased further and remained elevated longer compared with the meal containing glucose alone. The relative area under the insulin response curve was greatest following ingestion of the meal containing cottage cheese (360%) and was least with egg white (190%) compared with that following glucose alone (100%). The glucose response was diminished following ingestion of the meals containing protein with the exception of the egg white meals. The peripheral glucagon concentration was decreased following ingestion of glucose alone and increased following all the meals containing protein. The alpha amino nitrogen concentration varied considerably. It was decreased after glucose alone, was unchanged after egg white ingestion, and was greatest after ingestion of gelatin. The free fatty acid concentration decrease was 4- to 8-fold greater after the ingestion of protein with glucose compared with ingestion of glucose alone.