The envelope glycoproteins of Semliki Forest virus (SFV), Vesicular Stomatitis virus (VSV), and Influenza Fowl Plague virus (FPV) are vectorially targeted in neurons to the plasma membrane of dendrites (SFV and VSV) and axons (FPV). To gain insight into the mechanisms responsible for such polarized delivery we have examined the effects on neurons of nocodazole and brefeldin A (BFA), which are known to cause microtubule depolymerization and disassembly of the Golgi apparatus, respectively. Nocodazole treatment blocked transport of all viral glycoproteins to both axons and dendrites. BFA treatment induced disruption of the Golgi complex, including the trans-Golgi network (TGN), and tubulation of endosomes. However, the delivery of the SFV and FPV glycoproteins to the cell surface was not affected significantly by BFA, although processing and sorting were altered, as revealed by surface biotinylation and immunofluorescence microscopy of fixed nonpermeabilized cells. These results demonstrate the involvement of microtubules in axonal and dendritic transport of integral membrane glycoproteins, and the existence of a BFA-sensitive component in the sorting but not in the transport machinery.