Needle electromyography (EMG) has been an important diagnostic tool, although discomfort may limit its use in some children. We investigated the diagnostic utility of the clustering index (CI) method, a quantitative analysis for surface EMG (SEMG), in children. SEMG was recorded from the tibialis anterior muscle. Discriminant analysis between patients with neurogenic disorders and patients with myopathy was performed for whole epochs by using the CI and area values. Forty-five children (29 with myopathy, 16 with neurogenic disorders; age 9 ± 3.9 years) were enrolled. The mean discriminant function value of the neurogenic group was 0.58 ± 0.88 (-0.48-2.30), whereas that of the myopathic group was -0.55 ± 0.70 (-2.38-0.68). When the cutoff value was set at the limit of the other group, 17 of 29 children with myopathy and 7 of 16 children with neurogenic disorders were correctly classified. The CI method can be a useful noninvasive diagnostic tool in children with neuromuscular disorders. Muscle Nerve 58:824-827, 2018.