An automated technique for estimating the channel open time of human end-plate acetylcholine receptors (AChR) is described. The method, which is based on the power spectral analysis of electromyographic end-plate noise, is simple and permits a rapid estimation of the dominant AChR ion channel kinetics. Values of AChR channel open time determined by spectral analysis of end-plate noise in adults (1.23 +/- 0.01 ms at 33 degrees C) were consistently shorter than those estimated from the decay phase of extracellularly recorded miniature end-plate potentials. The channel open time extracted from the end-plate noise compared well with that derived from the analysis of in vitro recorded acetylcholine-induced current noise. Therefore, spectral analysis of end-plate noise may provide a good estimation of the kinetics of the human AChR ion channel. The technique is particularly useful in identifying congenital myasthenic syndromes with altered AChR ion channel function.