The protein composition of Trichomonas vaginalis isolates was evaluated using one-dimensional and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. At least two hundred intrinsically labeled and about 30 major extrinsically labeled proteins of molecular weights less than 120,000 were resolved by isoelectric focusing and electrophoresis. In general, long-term grown and fresh isolates of T. vaginalis gave similar fluorograms of the readily detectable proteins. Only a minor variance in a distinct protein was noted among three of the four fresh isolated tested. Labeling with [35S]methionine or 3H-amino acids gave almost identical profiles, ensuring the efficient radiolabeling of trichomonad proteins that dominate quantitatively. Comparative analysis of radioactivity profiles of one-dimensional gels emphasizing the region of high-molecular-weight proteins known to reside in low copy number revealed the presence or absence of the internally synthesized proteins from surfaces of T. vaginalis isolates. Finally, immunoblotting of two-dimensional gels demonstrated the highly immunogenic nature of proteins corresponding to quantitatively dominant molecular weight regions of intrinsically labeled proteins.