Hydrolyzed fish protein was prepared from five species of common Philippine market fishes. The process followed has the advantage of inverting any kind of fish flesh into hydrolyzed protein, a product which is best recommended for special diet therapy, as an important supplement to diets of convalescent patients and as medications to specific types of ulcer. Hydrolyzed fish protein also makes possible the utilization of cheap species of fish particularly those with low commercial value into high quality protein foods.