In the present study fast axonal transport was examined in streptozotocin rats with 4 weeks duration in diabetes. Tritiated leucine and 14C-labelled glucosamine were injected into the fifth lumbar ganglion and TCA-soluble as well as insoluble activity were measured in segments of the sciatic nerve at various time intervals. (1) Time from injection until start of fast axonal transport was prolonged in diabetic rats whereas anterograde transport velocity was unchanged. (2) Incorporation of labelled leucine was reduced by 40%, whereas labelled glucosamine incorporation was unchanged. (3) Alterations observed in accumulations of labelled glycoconjugates proximal and distal to a collection crush might represent a decreased amount of retrograde transported material. The changes found in protein and glycoconjugate synthesis and transport could be related to the early reduction in axon calibre and conduction velocity in peripheral nerve of streptozotocin-diabetic rat.