Recent advances in Satellite Laser Ranging (SLR) allow us to determine an improved value of the geocentric gravitational coefficient (GM) of 398600.4419+/-.0002 km3/sec2 (one sigma). This value is based on recent SLR observations of the LAGEOS I satellite; it is confirmed by observations of LAGEOS II, and is supported by results from Starlette, albeit at a lower level of precision. The information from these other satellites helps to support our claim of a conservative error estimate for GM, which amounts to about one half of a part per billion (ppb). Our determination of GM with the span of LAGEOS I data originally used to determine the current IERS92 standard (398600.4415+/-.0008 km3/sec2) gives approximately the same value at about the same uncertainty quoted by the authors in 1992. The improved value that we suggest falls well within the two-ppb error of the current standard, but differs from it by more than the error of the new estimate. The precision of the estimate of GM from SLR observations has improved by an order of magnitude in each of the last two decades. ¿ 1999 American Geophysical Union