The Relaxometer is a computer-controlled system developed for reliable clinical experimental measurements on neuromuscular block. This system is based on an adapted personal computer (Atari 1040 ST) with a monochrome monitor (Atari SM 124), and a microcomputer-driven slave unit (stimulator). There are several stimulation patterns available: single twitch at 0.1 and 1 Hz, single train-of-four, continuous train-of-four every 12 seconds, and tetanic stimulation at 50 Hz for 5 seconds followed by posttetanic count. The system is equipped with a temperature module for continuous monitoring of the skin/muscle temperature and a rechargeable battery to allow uninterrupted measurements if the apparatus is disconnected from the line power. All acquired data, computer-calculated parameters (onset time, duration time, recovery index, train-of-four ratio, tetanic fade, and posttetanic count), and the mechanomyogram are presented on screen continuously, are stored on floppy disk, and can be printed in a well-organized format.