Matrices are developed in order to convert published chlorophyll concentrations to values which would have been obtained had correct spectrophotometric equations been used. The main result is to decrease chlorophyll a values by as much as 23 % and chlorophyll a values by as much as 78 %. Corrected average values are given for the South-East Indian and South-West Pacific Oceans. Corrected values are given of the productivity index of several regions in the South-West Pacific Ocean. Some published values for the chlorophyll content of marine algae are corrected.