Techniques using alternative solvents to the standard acetone extraction procedure are superior and may become widely used for chlorophyll analysis. Dimethyl sulfoxide/acetone and dimethylformamide offer similar advantages of quick, efficient extraction. However, comparisons of methods using these solvents with the method using acetone demonstrated that for the efficient analysis of natural phytoplankton assemblages, glass-fiber filters should be extracted with maximum exposure to solvent. Storage of extracts is not recommended but if necessary, storage should be at −20°C. Furthermore, all investigators proposing to replace the acetone extraction with one of these methods are advised to perform similar comparisons before adopting either alternative.