The effect of major pigments on the absorption characteristics of phytoplankton were evaluated by comparing the in vjvo absorption spectra of phytoplankton with pigment data obtained using high-performance liqu~d chromatography (HPLC) for samples of phytoplankton collected in the northwestern Atlantic Ocean, during spring. Four groups of spectra having distinct absorption characteristics and well-defined regional distributions were identified. The result of using general parameters to estimate the absorption coefficient of phytoplankton from any region, the 'general approach', was compared with the result of using specific parameters for each region, or the 'regional approach' Two methods of estlrnating the absorption coefficient were tested for each approach. These were: a 'slnglepigment' method (Prieur & Sathyendranath 1981, Limnol Oceanogr 26:671-689), and a 'multi-pigment' method (Hoepffner & Sathyendranath 1991, Mar Ecol Prog Ser 73:ll-23). It was shown that the regional approach performed better (<10% average error) than the general approach (~2 0 % average error). Nevertheless, the results given by the general approach could be acceptable for some applications. The multi-pigment and the single-pigment methods performed equally well in the context of the reglonal approach, whereas in the general approach, the s~ngle-pigment method gave better results than the multi-pigment method. Overall, it appears that part~tioning the oceans into regions according to their absorption characteristics should improve regional models of light transmission and the algorithms for detection of pigments by remote sensing.