In the linear phase of growth, races B and L of Botryococcus braunii synthesized (6R)-~,E-carotene (6 and 6% of total carotenoids), ~,~-carotene (6 and 18%), echinenone (16 and 12%), (3'R)-3'-hydroxy-echinenone (14 and 0.5%), canthaxanthin (12 and 2%), (3R,3"R,6'R)-Iutein (22 and 29%), (3R,3'R)-zeaxanthin (4 and 7%), (3S,5R,6S,3"S,5'R,6"S)-violaxanthin (5 and 11%), (3R,3'R,6'R)-Ioroxanthin (9 and 10%) and (3S,5R,6R,3"S,5'R,6"S)-neoxanthin (6 and 5%), respectively, Secondary carotenoids produced in the stationary phase of growth were echinenone (28 and 20% of total carotenoid) and canthaxanthin (46%). Biosynthetic considerations for the primary and secondary carotenoids are made. It is suggested that the relative amounts of echinenone and canthaxanthin vs primary carotenoids reflect the physiological stage of the cells.