Walsh JC, Irwin MS, Weiss ZD. Recurrent idiopathic painless shoulder weakness in a Navy F/A-18 aviator. Aviat Space Environ Med 2013; 84:1–3.Brachial plexopathies of various etiologies are commonly discussed in the literature; however, recurrent painless shoulder weakness is an uncommon event, especially in an otherwise healthy adult man. A designated Naval F/A-18 E/F aviator presented with acute right-sided, painless shoulder girdle weakness that initially presented 2 yr earlier in a similar fashion. Extensive medical workups during both episodes did not reveal any identifiable cause. This case report discusses the most common etiologies of shoulder weakness. Additionally, we discuss the aviator’s most recent presentation and evaluation for acute shoulder weakness. Lastly, we propose a hypothesis as to the cause of the patient’s symptoms based on a review of the literature.