The paleorelief of mountain belts can be estimated from the δ18O value of authigenic minerals. Development of relief during mountain building often creates lee-side rain shadows in which precipitation is depleted in 18O and D. The magnitude of this rain-shadow effect is strongly correlated to relief. A compilation of δ18O data from surface waters throughout the globe shows a linear relationship between net elevation change and Δδ18O (R2 = 0.79). Through the use of this relationship, we investigated the timing and magnitude of elevation change in the Southern Alps of New Zealand and the Sierra Nevada of California. The δ18O values of kaolinites from New Zealand show an ∼6‰ decrease in the early Pliocene that corresponds to an ∼2 km elevation change in the Southern Alps. The δ18O of smectites from the Sierra Nevada show little change since 16 Ma, suggesting that these mountains have been a long-standing topographic feature.