Communications Research Laboratory has established four space geodetic observation sites in and around Tokyo, Japan under the Key Stone Project. At each of the four sites, an 11-m antenna VLBI system, a 75-cm telescope SLR system, and a geodetic GPS receiver are collocated closely. Site coordinates of the four VLBI stations have been connected to the ITRF96 reference frame from seven tie VLBI experiments with the 34m antenna station at Kashima by using its coordinates as the reference. GPS measurements at four Key Stone Project observation sites began in July, 1997. The GPS antenna positions were estimated by using ITRF96 site coordinates of the surrounding seven IGS sites. Regular SLR observations began in October 1998, and the site coordinates of four sites have been determined from a global solution. These results coincided within a few centimeters by using the results from local ground survey measurements. However, there remained discrepancies of a few centimeters and the cause of the discrepancies will be discussed. The precise comparison of the site velocities determined from VLBI and GPS measurements is also becoming possible and the results will be presented.