We have systematically measured the differential stress-optic coefficient, DeltaC, in a number of poly(methyl methacrylate) (PMMA) fibers drawn with different stress, ranging from 2 up to 27 MPa. DeltaC was determined in transverse illumination by measuring the dependence of birefringence on additional axial stress applied to the fiber. Our results show that DeltaC in PMMA fibers has a negative sign and ranges from -4.5 to -4.5x10(-12) Pa(-1), depending on the drawing stress. Increase of the drawing stress results in greater initial fiber birefringence and lower DeltaC.