Abstract: An experiment of Indiana limestone has been conducted for estimation of preexisting stresses in rock cores.Five cylindrical specimens were pre-stressed under triaxial loading conditions to simulate various in situ stress fields.26 pieces of specimens smaller,prepared from five pre-loaded rock specimens were under uniaxial pressure,when,acoustic emissions (AE) and applied stress were recorded as a function of time.The AE activity was presented as the sum of AE counts at each increment of 500 lbs.It was found possible for each experiment to fit a set of three straight lines to data obtained by using least square method.The value of stress at two intersections of these three lines.may serve to predict the levels of the maximal preexisting axial stress and confining pressure.The error for this technique may be found to be within 10% for most of specimens in use.