Kernco, Inc. was selected to design the Cesium Atomic Frequency Standards (CAPS) for the GPS Block IIR NAVSTAR satellites. These spacecraft are scheduled to be launched in the mid-1990s to replenish and upgrade the existing constellation of Global Positioning System satellites. The Block IIR CAFS output frequency is 13.4003378 MHz, the 686th submultiple of the cesium atomic resonance frequency. Using an integer submultiple simplifies the design of the atomic frequency standard's rf multiplier circuits, eliminating the secondary frequency synthesizer needed in previous designs. This paper describes the GPS Block IIR CAFS design, particularly the improvements made on our earlier Block 11 design. Test results are included.