The kinetics of DMS production resulting from reaction of OH- with DMSP were investigated as a function of hydroxide concentration and temperature. The reaction was first-order with respect to DMSP and OH-. The second order rate constant at 20+/-1 ¿C is 0.0044 M-1 sec-1. The activation energy for this reaction is 14.4 kcal mole-1. Our investigation indicates that the rate of reaction of DMSP with OH- is very slow at the pH of seawater (half-life of about 8 years at 10 ¿C), suggesting that DMSP, which may be a major precursor of DMS in seawater, decomposes in the ocean by other mechanisms. We have cultured a bacterium which produces DMS from DMSP quantitatively at rate many order of magnitude higher than indicated by OH-1 decomposition, suggesting that enzymatic processes accelerate the production of DMS from DMSP in seawater. ¿ American Geophysical Union 1987