The concentration of cosmogenic nuclides in rocks exposed at the Earth's surface is proportional to the total duration of their exposure. This is the basis for bedrock surface exposure dating and has been used to constrain valley lowering rates in the Taroko gorge, eastern Central Range, Taiwan. Taroko gorge contains a uniquely complete geomorphic record of fluvial valley lowering: continuous, fluvially sculpted surfaces are present in the lower 200 m of this marble gorge. Assuming no post‐fluvial erosion of the gorge wall, the concentration of in situ ‐produced cosmogenic ³⁶ Cl measured in gorge wall marbles reveals exposure ages from 0·2 ka in the active channel to 6·5 ka at 165 m above the present river. These ages imply an average fluvial incision rate of 26 ± 3 mm a ⁻¹ throughout the middle and late Holocene. Taking into account lateral gorge wall retreat after initial thalweg lowering would give rise to calculated older exposure ages. Without considering gorge wall retreat, our estimates therefore represent maximum incision rates. Estimated maximum Holocene incision rates are higher than the long‐term exhumation rates derived from fission track dating. The long‐term gorge development governed by tectonic uplift is superimposed by short‐term variations in incision rates caused by climatic or regional tectonic changes. Copyright © 2005 John Wiley & Sons, Ltd.