Xybion Corporation has developed an airborne multispectral measurement system (AMMS) as part of a small business innovative research contract with the Department of Commerce. The AMMS is a low-cost portable system that can provide multispectral data suitable for frequent measurement and mapping. It has been used for measurement of estuarine concentrations of chlorophyll and suspended sediments and mapping of submerged aquatic vegetation fields. Other applications include the identification of tree and plant species, the detection of crop stress, and the detection of man-made objects in a background of vegetation. The AMMS provides high spatial resolution multispectral image data in six user-defined bands in the 400- 900 nm wavelength region. The AMMS includes a highly innovative, computer-controlled, intensified, multispectral video camera (IMC), a spectroradiometer, a S-VHS VCR, and a portable IBM-PC-compatible computer system. An airborne trial over Cheseapeake Bay in June 1990 showed its ability to detect variations in water parameters. Simultaneous measurements from a ship provided sea-surface data, including continuous fluorometer readings, and discrete samples of chlorophyll, suspended sediments, and several other water parameters. Two spectroradiometers were included in the airborne equipment. One pointed downward to provide a high-resolution spectrum of a large water area under the plane. The other spectroradiometer measured downwelling irradiance. This allowed for conversion of the upwelling radiances measured by the IMC into reflectances. Calibrations for the IMC and the spectroradiometers were done before and after the trials. The results of this airborne trial are presented.