A well-known geophysical phenomenon, the postglacial rebound in Fennoscandia, is investigated by data from the Baltic Sea Level Project GPS Campaigns in 1993 and 1997. Preliminary results indicate that the estimated uplift rates vary from 1 mm yr-1 to 11 mm yr-1 with standard errors of the order of 1--3 mm yr-1, which is partly consistent with traditional terrestrial data. In addition, there is a horizontal component of plate motion of 21¿1 mm yr-1 towards northeast. After subtracting the average velocity, differential horizontal velocities suggest that there is a right-hand strike slip fault with a relative velocity of about 1.5¿0.5 mm yr-1 along a N-S direction in the middle of the Baltic Sea, which agrees with some geologists' belief of N-S trending 1.9-1.8 Ga old strike-slip megashears in the Baltic shield. ¿ 1999 American Geophysical Union