Ion channel transcripts from three genes were localized by the method of tissue in situ hybridization. The genes examined were theDrosophilaNa+channel genes,paralytic (para)andDrosophila Sodium Channel (DSC), and the K+channel gene,Shaker (Sh). All three of the genes were expressed in cell bodies of the fly central nervous system, including optic lobes, central brain, suboesophageal ganglion, and thoracicoabdominal ganglion.Shwas additionally expressed in the photoreceptor cells of the retina and pupal flight muscle, whileparaandDSCwere not. The temporal expression pattern ofShin muscle was different from that in the central nervous system: muscle expression was transient and limited to mid-pupal stage while nervous system expression was observed throughout pupation, apparently peaking at the late-pupal stage. Only one class of 5′end was found in pupal muscle, possibly indicating regulation of splicing pathways.