The Loma Prieta earthquake of 1989 provided an opportunity for a sensitive test of suggestions that earthquakes may be preceded by variations in Earth tidal strain amplitudes. Such variations have been proposed as providing an advantageous technique for detecting precursory changes in elastic parameters in a seismogenic zone. We have analyzed data from two borehole strainmeters continuously operating within 40 km of the epicenter and within about 10 km of the southern end of the rupture. We are unable to identify any precursory changes in M2 and O1 tidal amplitudes and estimate that any large scale changes in Young's modulus must have been less than about 2%. If these results apply generally, we would conclude that variations in elastic material properties prior to earthquakes do not occur throughout substantial volumes of the subsequent hypocentral region. ¿ American Geophysical Union 1992