Toxocara canis larval excretory-secretory antigens (TEX) were resolved by gradient pore polyacrylamide gel electrophoresis and analyzed using silver, periodic acid-Schiff, and immunoperoxidase stains. At least 15 bands between 29 and 94 kilodaltons (kDa) were detected by silver stain, all of which were recognized by antibodies in serum of a patient with visceral larva migrans. Immunoperoxidase stain detected an additional band at 92 kDa and 4-6 others above 200 kDa. Periodic acid-Schiff stain also detected the high molecular weight components, but did not detect constituents of approximately 53 and 57 kDa. Immunoperoxidase stain using antibody from the vitreous fluid of an ocular larva migrans patient detected 2 TEX components, approximately 76 and 80 kDa. Antigens were compared with respect to batch of larvae and age of larvae in culture. Qualitative differences that correlated with batch were found in the number of constituents above 200 kDa, and in 1 component of 78 kDa. Qualitative differences were noted in many minor components, some of which appeared to correlate with age of larvae in culture. Major TEX constituents were recognized consistently by antibody, regardless of batch or age of larvae. Total protein production per larva was approximately 8 ng/day, and was consistent over time. There was no evidence of neutral proteases in TEX.