We recognize Malory's greatest secular knights by the feats of arms they perform; Launcelot, Tristram and Gareth all sustain and inflict bloodshed to win many duels and tournaments. Yet Malory shows these three chivalric paragons bleeding profusely not only on the battlefield, but also in the bedroom. Each knight has a forbidden encounter with a lady when he is wounded – Tristram with the wife of Sir Segwarydes, Launcelot with Guenevere in ‘The Knight of the Cart’, and Gareth with Lyonesse – and all three episodes show male blood circulating to a very different effect than is ordinarily permitted or promoted in the Morte Darthur's literary and cultural milieu. When these knights sleep with their lovers – or try to, in Gareth's case – the results are transgressive on more levels than that of adultery. Malory writes of beds and bedsheets drenched with male blood in a way that explores the limits of knightly identity. My aim is to analyze this motif, and to address the ways in which it inverts the normal gendered views of the nature of blood flow to signal threats to or loss of the individual knight's social status. The manifestations of this motif are further transgressive in their tendency to develop into representations of female desire that seem unusually well developed when compared with the male-dominated norms of lust in medieval romance. This motif is not unique to the Morte Darthur, as we shall see; however, Malory's use of it is distinctive, not least because he uses it more than once, with the result that his text generates meaning not only in each of the motif's manifestations but also between them.