We describe the performance characteristics and frequency measurements of two high-accuracy high-stability lasercooled atomic frequency standards. One is a 657-nm (456-THz) reference using magneto-optically trapped Ca atoms, and the other is a 282-nm (1064-THz) reference based on a single Hg + ion confined in an RF-Paul trap. A femtosecond mode-locked laser combined with a nonlinear microstructure fiber produces a broad and stable comb of optical modes that is used to measure the frequencies of the reference lasers locked to the atomic standards. The measurement system is referenced to the primary frequency standard NIST F-1, a Cs atomic fountain clock. Both optical standards demonstrate exceptional short-term instability ( 5 10 15 at 1 s), as well as excellent reproducibility over time. In light of our expectations for the future of optical frequency standards, we consider the present performance of the femtosecond optical frequency comb, along with its limitations and future requirements. (NIST)], Boulder, CO, where he is currently a NIST Fellow and Ion-Storage Group Leader in the Time and Frequency Division. His research has concentrated on laser cooling and spectroscopy of trapped atomic ions with applications to atomic clocks, cold plasmas, and fundamental tests. More recent work has focused on quantum-state engineering with applications to quantum information processing and quantum-limited measurements.