Smooth muscle contraction is critical to peristalsis in the human esophagus, yet the nature of the channels mediating excitation remains to be elucidated. The objective of this study was to characterize the inward currents in human esophageal smooth muscle cells (HESMCs). Esophageal tissue was isolated from patients undergoing surgery for cancer, grown in primary culture, and currents were recorded using patch-clamp electrophysiology. Depolarization elicited inward current consisting of transient and sustained components, activating positive to -40 mV and peaking at 0 mV. Conductance was half-activated at -16 mV and half-inactivated at -67 mV. The transient current was abolished by removal of bath Na⁺ or application of tetrodotoxin (IC₅₀~20 nM), whereas it persisted in the absence of bath Ca²⁺ or the presence of Cd²⁺. These data provide evidence that cultured HESMCs express voltage-dependent Na⁺ channels. RT-PCR revealed mRNA transcripts for Na_x, the "atypical" isoform, as well as Na_v1.4. These studies provide the first evidence of Na_v1.4 in smooth muscle, and contribute to a model of excitation in HESMCs.