B104 neuroblastoma cells are excitable, but the ion channels underlying electrogenesis in these cells have not been identified. RT-PCR, restriction enzyme analysis and in situ hybridization were used to study sodium channel mRNAs in B104 cells. High levels of sodium channel alpha-subunit mRNAs III, NaG and Na6 and beta 1-subunit mRNA were detected by RT-PCR in B104 cells. Low levels of types I and II alpha-subunit mRNAs were also present. In situ hybridization with subtype-specific riboprobes detected sodium channel alpha-subunit mRNAs III, NaG and Na6 and beta 1-subunit mRNA in B104 cells; analysis of the percentage of B104 cells expressing each alpha-subunit mRNA subtype suggests that some cells express the mRNAs for several alpha-subunits.