We have investigated the rate of anterograde axonal transport of affinity-purified [125I]wheat germ agglutinin (WGA) in chick retinal ganglion cells. By 2 lines of evidence, we found the rate to be 22-44 mm/day. This rate is slower than that reported for many other endogenously synthesized proteins or for horseradish peroxidase, the only other exogenously supplied protein studied as an anterograde transported marker. This difference in rate of transport of [125I]WGA may reflect a novel pathway important in membrane recycling.