We have been attempting to improve estimates of long-term earthquake recurrence probabilities along the San Andreas Fault by means of synthetic seismicity calculations. The calculations are based on the concept of fault segmentation and incorporate the physics of static dislocation theory. Forecasts constructed from synthetic seismicity are robust in that: they embody regional seismicity information over several units of magnitude; they tie together in a physical manner, a spectrum of fault segment features such as length, strength, characteristic magnitude, mean repeat time, and slip rate; they can reasonably account for fault segment interactions; and they are formulated from a catalog which can be extended as long as needed to be statistically significant. We contend earthquake recurrence is more aperiodic than previously thought and, as a result, probabilities of major San Andreas earthquakes should be revised downward. ¿ American Geophysical Union 1993