Oceanic dimethylsulfide (DMS) is the major natural source of sulfur to the atmosphere. The equatorial Pacific Ocean is a region of relatively high DMS emissions that persist throughout the year. Measurements from 11 cruises between 1982 and 1996 show that the mean surface seawater DMS concentration in this region (15 ¿N to 15 ¿S) is relatively constant both seasonally and interannually (2.7¿0.7 nM). The large interannual variations in oceanic and atmospheric properties associated with El Ni¿o-Southern Oscillation (ENSO) events appear to have little effect on the concentration of DMS in surface ocean waters.