The Lense-Therring effect, a tiny perturbation of teh orbit of a particle caused by the spin of the attracting body, was accurately measured with the use of the data of two laser-ranged satellites, LAGEOS and LAGEOS II, and the earth gravitational model EGM-96. The parameter mu which measures the strength of teh Lense-Therring effect was found to be 1.1 plus or minus 0.2; general relativity predicts mu = 1.