Because of the variable effect on the altimeter height processing produced by a constant error in the altimeter time tag, the accuracy of the time tag is an important factor in the applications of the 10-cm SEASAT altimeter data. An assessment of the internal delays inherent in the altimeter microprocessor suggested that -79.4 ms should be added to the time tags transmitted to the ground receiving stations. To ensure the validity of this value, analyses were undertaken with the altimeter data. Two methods were used in these analyses which benefited from a global data distribution in the oceanic areas. These methods were (1) the crossover method which used altimeter data differenced at points where the SEASAT ground track intersected with itself and (2) the direct use of the altimeter data. The former method is independent of errors in the geoid model; hence it is considered to produce the most reliable results. Using the crossover method and several different ephemerides, various values of the time tag bias were estimated. For all crossover results the adopted value of -79.4 ms is within the bounds of the standard deviation associated with the estimates. In particular, the estimate of -78.1¿2.0 ms is considered to best represent the se tof estimated values.