We have estimated the Chandler frequency from a variety of polar motion time series derived from optical and space geodetic data which span various time periods from 1846 through the early 1990s. Estimates of F vary, depending upon which time series is employed, but the variation is not significant when associated intervals of confidence are considered; thus there is no evidence that the true Chandler frequency has varied. Using a maximum likelihood method, our preferred estimate of F is 0.8433 cycles per tropical year (cpy), ¿0.003 cpy, or equivalently a period of 433.1 mean solar days (msd), ¿1.7 msd. Estimates are given on the condition that the Gaussian statistical model of the excitation process is valid, and new approaches which employ observations of the polar motion excitation process should eventually provide better estimates, which may differ from those determined here.¿ 1997 American Geophysical Union