Spontaneous hyphaema in patients on systemic anticoagulants has been described in normal eyes and also in eyes with certain intraocular lenses following cataract surgery. These cases are rare and in all the reported cases the hyphaemas resolved without sequelae. Four cases are reported here of spontaneous hyphaemas in previously abnormal eyes of patients on anticoagulants. Three of these patients suffered considerable pain as a result of this. The reasons for this are discussed and early ophthalmic referral recommended if a hyphaema is suspected in these situations.