Site velocities in the Solomon Islands from Global Positioning System measurements spanning two years provide direct evidence of active deformation between the Pacific Plate and the Solomon Arc block. Convergence is occurring at the San Cristobal Trench at a rate of ~52¿4 mm/yr, with no apparent local deformation occurring in the Australian Plate at a distance of ~100 km from the trench. The islands of Guadalcanal and Makira are in a first approximation moving with the Pacific Plate although there is evidence of small but significant decoupling from the Pacific Plate of 14--23 mm/yr in a direction of 75--85¿. ¿ 1998 American Geophysical Union