In the literature nerve injury is not frequently considered a problem in proximal humeral fractures. Only a few studies exist concerning traction injury of nerves in fractures of the proximal humerus after low-velocity trauma. Almost all of them are retrospective and did not use electromyography. Patients with identical fractures can show quite different outcomes, which vary between complete recovery and severely limited shoulder function. On the assumption that nerve lesions can play a role in the recovery of conservatively and operatively treated proximal humeral fractures, we started a prospective follow-up study with electromyographic investigation. For this study, 143 consecutive proximal humeral fractures due to low-velocity trauma were included. According to the Neer classification, 93 were nondisplaced and 50 were displaced fractures. Denervation on the electromyogram was found in 96 patients (67%). The nerves most frequently involved were the axillary nerve (83 [58%]) and the suprascapular nerve (69 [48%]). Frequently a combination of nerve lesions was seen. Nerve lesions were much more frequent in displaced fractures (82% [41/50]) than in nondisplaced fractures (59% [55/93]). Complicating nerve lesions in patients older than 20 years of age were seen in about the same percentage of patients per decade. Nerve injury and the corresponding loss of muscle strength recovered well in all patients; however, the duration of the recovery was prolonged in cases with nerve lesions. Restoration of the function of the shoulder was less favorable. It is important to realize that, in both conservative and operative treatment of proximal humeral fractures, a paresis due to nerve injury can affect the restoration of shoulder motions. An electromyogram can be useful in the investigation of nerve lesions, because detection only by clinical examination proved to be very difficult. Because of the favorable electrophysiological recovery, no indication for exploration of nerve lesions was present in this series of fractures due to low-velocity trauma.