Variations in crustal thickness from the Kazakh Shield to the north-central Tien Shan are determined by receiver function analysis of broadband teleseismic P waveforms recorded on the Kyrgyzstan Seismic Telemetry Network (KNET). The receiver functions are calculated using a time-domain deconvolution approach, and are interpreted in terms of a single crustal layer, with thickness determined by a grid-search comparison of observed receiver functions with synthetics. Crustal thicknesses average 42 km in the southern Kazakh Shield and increase to approximately 60 km in the Tien Shan. Together with mass balance calculations, these results are consistent with the hypothesis that the compensation of the central Tien Shan relative to the Kazakh Shield are accommodated by an Airy-type crustal root, with a modest (300 kg/m3) density contrast across the Moho. ¿ 1998 American Geophysical Union