The gel permeation chromatographic behavior of three asymmetric proteins-collagen, fibrinogen, and the prolate ellipsoid Iysozyme-was investigated using a variety of gel and highperformance liquid chromatographic media of various pore sizes and a wide range of flow rates. The time dependency of the elution patterns for columns and the partitioning of proteins between solvent and gel phases in batch experiments show that the "anomalous" behavior of asymmetric proteins is explicable by the mechanism proposed by Y. Nozaki, N. M. Schechter, J. A. Reynolds, and C. Tanford (1976, Biochemistry 15, 3884); i.e., that these proteins penetrate pores of a size comparable to the minor semiaxis of the protein by end-on insertion. Thus, native type I collagen behaves as if it were a spherical protein of radius 8.2 A, fibrinogen has an apparent radius of 32.4 A, and lysozyme has an apparent radius of 14.6 A. The rate at which asymmetric proteins penetrate the gel interior, however, is slow compared to the rate of gel penetration by globular proteins. The end-on insertion mechanism predicts that given infinite time, asymmetric proteins will be included into that portion of the internal volume of the gel which their smallest projectional cross sections allow them to penetrate. A method is presented for extrapolating the elution volume of asymmetric proteins to infinitely slow flow rate; from this extrapolation, one can calculate the minor semiaxis of the protein.