We determined the Δ18O and Δ13C of individual Globigerinoides ruber and Pulleniatina obliquiloculata from sediment traps located from 5 ¿N to 12 ¿S along 140 ¿W in the Pacific Ocean to evaluate the effects of varying <CO3=> on shell Δ18O and Δ13C. Variations in the offset between shell Δ13C and Δ13CDIC(ΔΔ13Cs-DIC) are attributed to differences in <CO3=>, temperature, and shell size between sample sites. When ΔΔ13Cs-DIC of G. ruber was corrected for variations in <CO3=> using the experimental slope of Bijma et al. <1998>, the residual ΔΔ13Cs-DIC was correlated with mixed layer temperature (+0.10¿0.04? ¿C-1). The slope of this temperature effect is consistent with experimental results. In P. obliquiloculata, ΔΔ13Cs-DIC and temperature were strongly anticorrelated (-0.14¿0.03? C-1). We are unable to separate the influences of <CO3=> and temperature in this species without independent experimental data. Correcting for <CO3=> variability on Δ18Os of G. ruber improves the accuracy of estimated sea surface temperatures. ¿ 2000 American Geophysical Union