The 1987 Crustal Deformation Survey of the Yellowstone-Hebgen Lake region produced accurate geodetic measurements in an area unique for its rugged topography and volcanic processes. Using the integrated geodesy approach, Global Positioning System (GPS) baseline vectors, geodetic leveling, and gravity measurements were combined in a simultaneous least squares adjustment. Using 30'¿30' digital terrain data, and an Airy model, isostatically corrected complete Bouguer gravity disturbances highlight both the Yellowstone Caldera and a second gravity low near Hebgen Lake. A linear relationship between these disturbances and the departures of geoid height from the Airy isostatic model have been found (r=0.84). Adjusting the covariance function while incorporating the GPS contribution yields a function whose correlation length is significantly longer than that predicted by autocorrelation statistics of the gravity disturbances alone. The integrated adjustment produced a geoid whose low-frequency components are in good agreement with OSU86F. Formal statistics indicate precision of 2--5 cm. GPS residuals for 35 leveled point sin the adjustment have a root-mean-square value of 2.9 cm and a standard error estimate of 4.6 cm. In comparison, a free adjustment of 152 GPS vectors yields a differential height standard error of 3.8 cm. ¿ American Geophysical Union 1991