Based on an analysis of drifter data from the World Ocean Circulation Experiment during 1979-1998, the sizes of the eddies in the North subtropical Pacific are determined from the radii of curvature of the drifter paths calculated by using a non-linear curve fitting method. To support the drifter data results, Sea Surface Height from the TOPEX/POSEIDON and ERS2 satellite data are analyzed in connection with the drifter paths. It is found that the eddies in the North Pacific (18°-23°N and 125°-150°E) move westward at an average speed of approximately 0.098 ms-1 and their average radius is 176 km,with radii ranging from 98 km to 298 km. During the nineteen-year period, only 4 out of approximately 200 drifters (2%)actually entered the South China Sea from the area adjacent to the Luzon Strait (18°-22°N and 121°-125°E) in the winter. It is also found that eddies from the interior of the North Pacific are unlikely to enter the South China Sea through the Luzon Strait.