A multiple electrophoretic method suitable for purification of type III collagen from a mixture of various collagen types is described. The technique is based on preparative electrophoresis in acid media and successive electroelution of the collagen fractions. By sodium dodecyl sulfate-polyacrylamide electrophoresis and immunoblotting, the collagen composition of the electroeluted fractions was characterized as a mixture of alpha (III), beta (III) and gamma (III) without any other visible contaminants. This technique enabled us to obtain large quantities of type III collagen from partial pepsin digests of human placenta suitable for further processing.