The Loma Prieta earthquake of October 17, 1989 was predicted by the use of two pattern recognition algorithms, CN and M8. The prediction with algorithm CN was that an earthquake with magnitude greater than or equal to 6.4 was expected to occur in a roughly four year interval starting in midsummer 1986 in a polygonal spatial window of approximate average dimensions 600¿450 km, encompassing Northern California and Northern Nevada. The prediction with algorithm M8 was that an earthquake with magnitude greater than or equal to 7.0 was expected to occur within 5 to 7 years after 1985, in a spatial window of approximate average dimensions 800¿560 km. The predictions were communicated in advance of the earthquake. In previous, mainly retrospective applications of these algorithms, successful predictions occurred in about 80% of the cases. ¿ American Geophysical Union 1990