The first attempts in computer aided EMG analysis were performed for the automatic evaluation of interference pattern. In the routine work the turn-amplitude analysis (T/A), introduced by Stålberg and Antoni (1981), proved to be an accurate and easily performed procedure, with the advantage of being relatively independent of force. The aim of our study was to determine the diagnostic significance of T/A analysis in various neuromuscular diseases. The recordings were performed with Madaus Amplaid EMG 15, and concentric needles were used. fifty subjects had been investigated. The diagnoses were based on clinical, biochemical and histological findings. Tibialis anterior, quadriceps femoris, extensor digitorum communis and biceps brachii muscles were regularly sampled. In myogenic conditions a distinct correlation was found between the severity of muscle damage and T/A values. The more pronounced abnormalities were observed in Duchenne boys. Except the ALS in neurogenic processes correlation was found between the severity of muscle damage and T/A analysis, too. The central lesions did not have any effect on the T/A results. Examples of the possible sources of technical errors were presented and comparisons to the traditional concentric needle EMG were done.