Background: Diseases in the peripheral motor unit are common in children. The term peripheral hypotonia covers disorders of the neuromuscular unit other than causes in the Central Nervous System (CNS). This includes the peripheral motor unit with its four components: Anterior horn cell in the spinal cord, its axons with other axis forming the peripheral nerve (including the cranial nerves) and the neuromuscular junction with the muscle fibers innervated by a single motor neuron. The aim of this work is to give a profile of the causes of peripheral hypotonia in infants and children attending Assiut University Children Hospital. Patients and Methods: 32 patients aged over one month to 14 years were assessed clinically and had creatine kinase enzyme measured, as well as Nerve Conduction (NC) and Electromyography (EMG), together with muscle ultrasonography done. Results: Cases had Guillan-Barre Syndrome (GBS) in 56.3%, Duchene Muscular Dystrophy (DMD) in 21.9% and Spinal Muscular Atrophy (SMA) in 12.5%, and myositis in 9.4%. Ultrasonography showed sensitivity in the diagnosis of peripheral hypotonia in 96.43% and specificity of 75%, with positive and negative predictive values as 87.5% and 12.5% respectively. Conclusion: For neurological cases, hope is present with early discovery of spinal muscular atrophy in newborns by screening with ultrasonography with new treatment by gene therapy because of higher sensitivity and predictive value. Recommendations: A future study in peripheral hypotonia in pediatrics is recommended with a bigger number of cases to support this work.