The ability of optimum multiparameter (OMP) analysis to identify regions where diapycnal mixing is prominent is examined. OMP analysis and isopycnal analysis are applied to synthetic data sets constructed with predetermined mixing regimes and ratios. Oceanic conditions are modeled by including random noise representative of environmental variability found in the eastern Indian and Atlantic Oceans. Comparison of results from OMP and isopycnal analysis verifies that in the absence of environmental variability, OMP analysis can isolate regions with moderate diapycnal mixing. When environmental variability is included, the effects of diapycnal mixing have to be strong enough to be detected without ambiguity. It is shown that this is the case in the eastern Indian Ocean and, most probably, also in the eastern Atlantic Ocean. ¿American Geophysical Union 1994