A series of stress measurements using hydraulic fracturing techniques were made in five holes drilled into shale along a line normal to, and 3--18 km from, the trace of the San Andreas Fault. In all the holes, except the one farthest away from the fault, the least principal stresses were found to be approximately equal to the weight of the overburden. The drilling as well as the variation in breakdown pressures suggested a more or less visco-elastic material. The data further suggested that the shale does not retain the regional tectonic stresses. The dip of most of the hydraulic fractures was greater than 69¿. Televiewer logs showed that the natural fractures have a consistent dip of 58¿ principally to the west-southwest. Although widely scattered, the orientations of the total set of natural and hydraulic fractures suggest that the direction of maximum principal stress is north-south. The strike of the San Andreas Fault is N45¿W, which falls within the limits of the relationship of stress distribution and fault trace predicted on the basis of the Mohr-Coulomb theory for strike-slip faults. It is suggested that more competent rocks would be better suited to a study of the relationship of tectonic stresses to the San Andreas Fault.