This study considers spatial and temporal changes of the stress regime during the 1983 Coalinga aftershock sequence. In both cases the observed changes manifest themselves as rotations of the most compressive stress axis. Inversion of 165 M≥3 aftershocks shows that in the southern aftershock zone the azimuth of the most compressional stress axis is oriented 24¿ E of north, while in the northern and central zones it is oriented 51¿ E of north. Statistical analysis by use of non-parametric bootstrap resampling shows that this rotation is significant at above the 95% confidence level. Inverting the focal mechanisms of 122 M≥3 aftershocks in the central and northern aftershock zones reveals a rotation of the principal stress axes during the first 500 days after the main shock. The compressional axis rotates from an azimuth of 62¿ E of north to 47¿ E of north. Statistical analysis by use of nonparametric bootstrap resampling shows that this rotation is just significantly different from zero at the 95% confidence level, subject to the assumption that 80% of the fault planes can be correctly picked from the two nodal planes. As the number of fault planes picked correctly varies from 50% (random choices) to 100% the significance of the rotation varies from 87% to 98%. Further investigation fails to find the signature of the stress changes predicted by dislocation theory in the focal mechanisms of the aftershocks. Active folds in the area suggest that the pre-main shock stress regime had a compressional axis with a NE-SW orientation. Thus the rotation during the aftershock sequence is thought to be a rebound from a stress anomaly induced by the main shock. This stress anomaly may be causally related to the occurrence of the aftershocks. ¿ American Geophysical Union 1987