Trains of neurally evoked compound electromyographic responses of the thenar muscles were studied in 20 patients anesthetized with enflurane and N2O and paralyzed with d-tubocurarine. Fade was correlated with stimulus frequency (0.1 to 50 Hz) and degree of neuromuscular block. The lowest response in a train occurred on the 4th and the 6th-to-8th responses when the train was elicited at 2 Hz and 50 Hz, respectively. Fade was more observable with deeper block and could best be demonstrated by 5 Hz stimuli. With 50 Hz stimuli, a concomitant facilitation, observable from the beginning of the train, partially compensated for the fade.