Comparative measurements of the ophthalmic arterial pressure have been performed in 102 eyes using the Mikuni dynamometer and the Stepanik-Arteriotonograph. There was a linear correlation between the results obtained with both methods (P less than 0.001). Ophthalmic arterial blood pressures taken with the Stepanik-Arteriotonograph (SAT) were on the average 23 mmHg higher than with the Mikuni suction cup dynamometer. The mean ophthalmic blood pressure using the SAT was 88% of the mean brachial arterial pressure, whereas it was 70% with the Mikuni instrument. Differences between duplicate readings in the same eye were higher with the SAT than with the Mikuni dynamometer (P less than 0.001). Differences between both eyes in one individual were on the average greater using the SAT than the Mikuni instrument (P less than 0.001) and suction cup dynamometry was tolerated better subjectively than ophthalmic arteriotonography. A different reference point for taking arterial blood pressure with both methods is discussed. In arteriotonography the point of pressure measurement is more central than in suction cup dynamometry, because of the different method of increasing intraocular pressure in each procedure. The pros and cons of both methods are critically discussed.