Our conception of Shakespeare is incomplete unless we recognize that, like every dramatist working in the London theatres between 1579 and 1642, he occasionally coauthored plays. Strong evidence now exists for his having worked with Peele on Titus Andronicus, Middleton on Timon of Athens, Wilkins on Pericles, and Fletcher on both Henry VIII and The Two Noble Kinsmen. Shakespeare's hand has also been reliably detected in The Book of Sir Thomas More and Edward III. This essay reexamines 1 Henry VI, bringing together and expanding the evidence that Nashe wrote Act 1. This attribution is based on the coincidence of several complex associations of idea and words in Nashe's work and in 1 Henry VI, some of which derive from books known to Nashe but not to Shakespeare. Stylistic markers shared by Nashe and the author of Act 1 include a staccato utterance, made up of short sentences and many questions; extensive syntactical inversion of subject and object; and distinctive prosodic features. The most likely scenario is that Nashe was involved in the first recension of the play, ca. 1592, and that Shakespeare took part in a revision, ca. 1594. A fresh examination of the scenes ascribed to Shakespeare confirms his hand in 2.4 and 4.2–4.5 and rejects the attribution of 4.6–7. A concluding survey of modern editions of 1 Henry VI reveals that most editors have been unwilling to engage either with the specific evidence for coauthorship or with attribution scholarship in general.