The advantages of monitoring neuromuscular blockade during anaesthesia and intensive care by electromyography or mechanomyography are reviewed. Correlations between clinical symptoms, monitoring parameters and percentage of receptor occupation are established. Single twitch, train of four and tetanic stimulation of motor nerves are described in detail and their relative indications discussed. It is pointed out, that neuromuscular transmission can be considered to be unimpaired, if single twitch responses equal 100% of preblock values and train of four ratios achieve 0.7. Especially under conditions of hypothermia, acid-base disturbances or side effects of drugs other than muscle relaxants monitoring of neuromuscular transmission is superior to simple clinical judgment.