In Dakar, during a definite period of time, all the new leprosy cases have been subjected to an electromyographic examination before treatment: a total of 37 patients and 518 examined nerves including all clinical forms: NCV: 33% of the examined nerves are found to be affected. The sensory nerves are frequently and early involved. In frequency order: sural (54%), posterior tibial (50%), sensory ulnar (35%), sensory median (29%), motor ulnar (28%), lateral popliteal (17%) and motor median (12%). The study of the SCV seems relatively more reliable than the sensory testing in the case of the ulnar and the median (75 comparisons): concordance in 69% of the cases; SCV only abnormal in 19%; sensory testing only abnormal in 12%. The EMG detection is superior to the motor testing and to the motor nerve conduction for the lateral popliteal (32 comparisons): 41% of concordant examination; 59% of differences among which 44% of anomalies revealed only by detection.