The effects of colchicine treatment on retrogradely-transported WGA-HRP were examined in the cat. The ventroposterolateral nucleus of the thalamus was bilaterally injected with WGA-HRP followed 2 days later by a unilateral injection of colchicine into the dorsal column nuclei (DCN). The cats were sacrificed by perfusion 24 h later. Retrogradely-transported WGA-HRP within DCN neurons was visualized in coronal, vibratome-cut sections of the medulla using the procedure of Rye and collaborators (J. Histochem. Cytochem., 32 (1984) 1145-1153). On the uninjected side, as expected, the reaction product filled numerous neuronal perikarya and their dendrites. In contrast, on the colchicine-treated side, the reaction product was restricted to dendrites; little labeling was observed within perikarya. These findings appear to reflect colchicine's effects on the translocation of lysosomes from neuronal perikarya to their dendrites are important for the interpretation of data from experiments using colchicine to enhance perikaryal immunohistochemical staining.