Previous electrophysiological work has demonstrated expression of a voltage-gated Na+ channel (VGSC) specifically in two highly metastatic prostatic epithelial tumour cell lines: MAT-LyLu (rat) and PC-3 (human). However, the identity of the channel(s) present was uncertain. The present study used a combination of molecular biological techniques to demonstrate that full-length skeletal muscle type 1 (SkM1) VGSC mRNA is present in the mRNA pool of the MAT-LyLu cell line. mRNA for this particular channel type was also expressed in the PC-3 cells. In situ hybridisation data suggested that the level and pattern of rSkM1 mRNA expression were different in the Dunning cells of markedly different metastatic potential. Interestingly, the same type of mRNA was also detected in the weakly metastatic counterparts of the cells: AT-2 (rat) and LNCaP (human).