We determined stable carbon isotopic composition (δ13C) of C2 to C9 dicarboxylic acids (DCAs) and some ketoacids in the marine aerosols from the western Pacific and Southern Ocean (35¿N to 65¿S). On average, oxalic (mean, -16.8?), adipic (-17.2?), and glyoxylic (-17.6?) acids showed heavier δ13C, whereas maleic (-24.2?), methylmalonic (-23.6?), and phthalic (-23.1?) acids were more depleted in 13C. Oxalic acid presented very diverse δ13C values (-27 to -7?), which increased from midlatitudes toward the equator. A similar latitudinal trend of δ13C was also found for malonic, succinic, and adipic acids. However, such a trend was not observed for phthalic, maleic, and glyoxylic acids. We suggest that the δ13C increase toward the equator is associated with photochemically aged air masses, in which kinetic isotope effects for photochemical degradation of DCAs may be important. Differences in δ13C of some saturated DCAs were also found to increase from midlatitudes to the equator.