Organic materials in the oceans have spectral signatures based on their light-scattering properties. These optical properties are related to bio-physical and bio-chemical data products such as the concentration of phytoplankton chlorophyll-α through bio-optical algorithms. A primary quantity of interest in ocean color research is the water-leaving spectral radiance L w(λ), often normalized by the incident solar flux. For quantitative studies of the ocean, derivation of the relationship between the optical properties and physically meaningful data products is critical. There have been a number of recent advances in radiometry at the National Institute of Standards and Technology that directly impact the uncertainties achievable in ocean-color research. These advances include a new U.S. national irradiance scale; a new laser-based facility for irradiance and radiance responsivity calibrations; and a novel tunable, solid-state source for calibration and bio-optical algorithm validation. These advances, their relevance to measurements of ocean color, and their effects on radiometrically derived ocean-color data products such as chlorophyll-α are discussed.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.