In situ sea level data from a shallow pressure tide gauge (mean depth 3.21 m) at Sao Tome Island, Gulf of Guinea, and altimeter data from TOPEX/POSEIDON (T/P) were analyzed and compared. The Texas model, a T/P-derived tide model, is used for the tidal correction of altimeter data. Sea level anomaly time series from both data sets were low-pass filtered by using a Gaussian recurrent interpolation scheme, suppressing high-frequency fluctuations of periods much less than 2 months. According to the 1992--1993 Sao Tome tide gauge data, a clear seasonal signal was observed both in 1992 and in 1993, presenting two sea level maxima in February and October and two minima in June and December. These sea level variations are consistent with the known seasonal mean sea level cycle of the area, most of which can be explained by steric sea level changes due to the seasonal cycle of upper 500-m water column properties in the Gulf of Guinea. On the basis of the 60-day low-passed tide gauge time series, significant year to year variations were observed as well, with a 6.3-cm sea level difference in February (+8.1 cm in 1992 versus +1.8 cm in 1993) and a 4.4-cm difference in October (+4.6 cm in 1992 versus +9.0 cm in 1993). Minimum sea levels, occurring just prior to the upwelling season (July--August), were almost the same for both years (-9 to -10 cm) but lasted much longer in 1992 (2 months) than in 1993 (2 weeks). During the 15-month period of concomitant observations, from October 1992 to December 1993, these seasonal and year to year sea level variations are remarkably well reproduced by the T/P sea level time series, with an rms difference of 2.2 cm and a correlation coefficient of 0.88. This result in the equatorial Atlantic is consistent with other intercomparisons in the Pacific and Indian Oceans. This excellent recovery of the oceanic signal is undoubtedly the result of unprecedented high precision of T/P measurements and the reliable T/P-derived tide model that is used in the present study.