Considerable variation was found in the success of extraction of chlorophyll pigment from different species of phytoplankton by grinding. The optimal conditions for chlorophyll a were established for Dunaliella tertiolecta, Thalassiosira nordenskioldii, Chaetoceros curvisetus, Fragilaria sp., and Phaeodactylum tricornutum. Significant conclusions could not be drawn for chlorophyll c because of the relative imprecision of the chlorophyll c measurement compared with chlorophyll a. For chlorophyll a, ease of extraction was inversely related to the dry weight chlorophyll a ratio.