A calibration experiment for the SEASAT radar altimeter was conducted in the Burmuda calibration area during September and October of 1978 by a group of Federal Government agencies, universities, and research organizations. As part of the SEASAT calibration activities, a tide gage was installed by the National Ocean Survey at an open coastal location on Bermuda to provide a determination of the instantaneous sea surface height during the SEASAT overflights of the island. The tide gage was geodetically tied to the laser tracking station on Bermuda, so that SEASAT's position relative to the sea surface could be determined independently and compared with the value provided by the altimeter measurements. The root sum square error in the determination of the vertical position of the laser, relative to the sea surface, has been estimated to be 4.0 cm exclusive of possible errors arising from the present lack of precise information on the elevation of the geoid at Bermuda.