Airborne Thematic Mapper data from the NERC MSS-82 campaign in Swansea Bay, Bristol Channel, have been correlated, in linear and multiple regression analyses, with measured water quality parameters: suspended sediment concentration ( SSC) mean grain size of material in suspension, surface salinity and chlorophyll-a concentrations. The investigation is an extension of that carried out by Collins and Pattiaratchi (1984). The spectral wavelengths providing maximum information on the distribution and concentrations of water quality parameters are determined. The conclusions reached are compared with those of other investigators. It is shown that particle size influences the spectral signature of suspended sediment, and that there is a masking effect of high SSCs on the spectral reflectance of chlorophyll. Multiple regression equations are derived and applied to the digital remotely-sensed data, to produce thematic maps of water quality. The maps are compared to the sea-truth data. It is concluded that airborne remote sensing provides a useful means of mapping surface water quality in coaslal regions.