SUNCT is a unilateral headache syndrome with shortlasting attacks, accompanied by e.g. conjunctival injection and lacrimation on the painful side. Intraocular pressure (lOP), corneal indentation pulse (CIP) amplitudes, episcleral venous pressure, and corneal, tympanic, and facial temperature have been studied in 6 SUNCT patients. IOP and CIP amplitudes increased on the painful side during headache paroxysms, while episcleral venous pressure remained unchanged. Corneal temperature seemed to increase during attack on both sides. However, the number of observations during attacks is scanty. Outside of attacks, the corneal temperature on the symptomatic side seemed to be higher when compared with the non-symptomatic side (generally ³0.5°C), provided that the attack frequency was high. The facial temperature seemed to be even on both sides or slightly higher on the symptomatic than on the non-symptomatic side in the periocular area. This pattern seems to be different from the one in trigeminal neuralgia, in which the temperature has been reported to be lowest on the painful side of the face. During attacks, there seemed to be a tendency for the temperature to increase in the periocular area, but not over the mandible or in the neck. The results obtained could be caused by increased blood supply to the eye (and the surrounding skin) on the symptomatic side because of vasodilatation during repeated pain attacks. As far as the ocular changes are concerned, probably the arteriolar side of the vascular bed is involved.