Book excerpt: A selected set of reprints from the Optical Frequency Measurement Group of the Time and Frequency Div. of the Nat. Inst. of Standards and Technology and consists of work published between 1987 and 1997. The 2 programs represented are (1) development of tunable diode-laser technology for scientific applications and precision measurements, and (2) research toward the goal of realizing optical-frequency measurements and synthesis. The papers are organized in 5 categories: diode laser technology; tunable laser systems; laser spectroscopy; optical synthesis and extended wavelength coverage; and multi-photon interactions and optical coherence.