The controlled release of drugs from gelatin hydrogel was studied undereffects of crosslinking ratio, gelatin type, namely porcine and fish gelatins, and drug size. The drug-loaded gelatin hydrogels, using glutaraldehyde as the crosslinker, were fabricated by solution casting, with salicylic acid, and 5-sulfosalicylic acid as the model drugs. The release mechanism and the diffusion coefficients of the drug from gelatin hydrogels were determined prusing a modified Franz-Diffusion cell and the Higuchi equation to determine the effects of the hydrogel and drug sizes.The time release profiles were obtained with the time exponent n close to 0.5, indicating the process was the Fickian diffusion. The diffusion coefficients of the model drugs decrease with decreasing hydrogel pore size and increasing drug size. The diffusion coefficients of the two model drugs and of both gelatinsdisplay a common scaling behavior: D = D0/(drug size/pore size)m with the scaling exponent m equal to 0.45 and with nearly the same D0.Both porcine and fish gelatins are thus shown to be equally effective drug release matrices with the same ease in preparation.