Carbon fiber-reinforced gelatin composites have been prepared in our laboratory to obtain a navel biomaterial of improved mechanical properties. The swelling behavior (swelling rate, swelling kinetics, maximum solvent uptake, etc.) for both continuous carbon fiber-reinforced gelatin composite (C-L/Gel) and short carbon fiber-reinforced gelatin composite (C-S/Gel) are investigated. Experimental data show that the swelling process of the original gelatin and gelatin matrixes in both composites follows a second-order kinetics. The swelling of the gelatin matrixes in both composites proceeds slower than that of the pristine gelatin, and depends on fiber form and fiber volume fraction (Vf). Results indicate that the presence of carbon fibers suppresses the swelling of the gelatin matrixes in both composites. It is found that the gelatin matrix in C-S/Gel possesses a smaller swelling rate and maximum solvent uptake than that in C-L/Gel. A mechanism governing these phenomena is discussed in this article. (C) 2000 John Wiley & Sons, Inc.