The Δ 13C of dissolved inorganic carbon (DIC) decrease (the 13C Suess effect) in the Indian Ocean was calculated using a multiparameter linear regression comparison of the 1978 Geochemical Ocean Sections Study and 1995 World Ocean Circulation Experiment Δ 13C of DIC, hydrographic, and nutrient data. The surface ocean Δ13C decrease rate along 80¿ and 115 ¿E ranged from approximately -0.1? decade-1 at 55 ¿S to a maximum of approximately -0.18? decade-1 at ~35 ¿S and decreased northward to around -0.13? decade-1 at the equator. Using a global extrapolation based on ocean model results <Bacastow et al., 1996> and previous Δ 13C changes calculated from 1970 to 1993 station reoccupations in the Pacific Ocean and based on preformed Δ 13C versus chlorofluorocarbon stage trends in the Indian, Pacific, and Atlantic Oceans <Sonnerup et al., 1999>, an ocean-wide average surface ocean Δ 13C rate of change of -0.15 to -0.17? decade-1 was estimated. The average depth-integrated Δ 13C change rate between 1978 and 1995 along 80¿ and 115 ¿E was -6.9¿0.5? m yr-1 from 58 ¿S to 5 ¿N. ¿ 2000 American Geophysical Union