An acceleration transducer elicits an output voltage proportional to the deformation of the piezo crystal, in accordance with the twitch responses of the applied fingers. The reliability of such a transducer was evaluated by comparing induced twitch responses with those from a force transducer applied on the contralateral arm of an individual during neuromuscular block with vecuronium. The results obtained from twitch responses with the acceleration transducer during neuromuscular block were almost identical to those obtained with the force transducer. Also, the twitch heights due to acceleration of the examined thumb correlated extremely well with the twitch height due to twitch tension with the force transducer. It is concluded that the acceleration transducer may be a useful and reliable device for monitoring neuromuscular block, although responses during tetanic stimulation such as tetanic fade cannot be determined by the transducer.