Forty-seven temperature sections taken in the equatorial region from at least 2°N to 2°S between 97°W and 178°E have been used to study the spreading of the thermocline in order to acquire further information about possible seasonal and longitudinal variations in the Equatorial Undercurrent. As evidenced by the spreading of the isotherms, the Undercurrent appears to be confined between 2°N and 2°S and to have its core near the 20°C isotherm, with both the isotherms and the current core shoaling eastward....