Data from 6 temperature sections are combined with other SEQUAL/FOCAL data along 4¿W from the coast (5¿N) to 3¿S to study the seasonal variation of the temperature field in the Gulf of Guinea during 1983. The equatorial upwelling begins during mid-April approximately 1 1/2 months before the climatic mean but has a normal amplitude and duration. The upwelling on the coast at Abidjan occurs approximately 1 1/2 months after the equatorial upwelling and preceds its climatic mean by 2 weeks. At the equator vertical displacements of isotherms within the thermostad are complicated by an anomalous warming of the thermostad in May. Between the thermostad and the deeper thermocline at 230 m the seasonal isotherm dispalcement amplitude has a minimum. At greater depths it increases again. In all respects the fluctuation of the thermal field at the equator is similar to the climatic mean but displaced forward in time by 1 1/2 months.