Hyphaema developed spontaneously in 16 of 458 patients with microbial keratitis treated at two centres on the East and West Coasts of the United States. Chronic corneal conditions were often present, and three cases had rubeosis iridis. Inflamed iris vessels were assumed to be the source of the haemorrhage. The hyphaemas tended to persist longer than is usual, particularly when coincident with a hypopyon. Recurrent hyphaemas are reported in two patients from outside this series. Spontaneous corneal haemorrhage was seen in three cases. Subepithelial bleeding settled rapidly, but a combined midstromal and pre-Descemet's haematoma cleared more slowly. Anterior segment bleeding was significantly associated with advanced age, female sex, infection with Gram-positive organisms, and hypopyon.