Side-firing fibers are used to provide coagulative therapy to the urologic tract. These fibers use different optical technologies to deflect the beam transverse to the fibers’ optical axis. This produces emitted beams which differ in both beam direction and divergence angles. The relative optical performance of 13 fibers was studied in an optical phantom suspension. The fluence rate distribution created by each side-firing fiber was determined. The fluence rate distribution accounts for both the direct and spurious beams emitted from side-firing fibers as well as the light scattering produced by the target tissue. Based upon limited clinical dosimetry studies, the relative fluence rate distribution appears to indicate general exposure conditions for the evaluated fibers.