All of the major carotenoids of Synechococcus sp. PCC 7002 were identified, including a new aromatic xanthophyll, χχ-caroten-18,18'-dioic acid, now called synechoxanthin. Synechoxanthin is a member of a family of χχ-carotenes found in a variety of cyanobacteria. The discovery of these compounds demonstrates synthesis of aromatic carotenoids by cyanobacteria and provides the first instance of an organism capable of de novo synthesis of χχ-carotenes. The functions of the CrtH lycopene isomerase, CrtR C-3-β-hydroxylase, CrtW C-4-ketolase were evaluated and verified. Phylogenetic analysis was used to identify additional genes of the carotenoid biosynthetic pathway in this organism. Among the new genes identified were cruA and cruP, which encode lycopene cyclases that belong to a new fourth family of lycopene cyclases and fill a major gap in the carotenoid biosynthetic pathway of cyanobacteria that lack the CrtL (plant-type) lycopene cyclases. Two new genes were identified in the myxoxanthophyll pathway, cruF, cruG. CruF and CruG are respectively a 1'-hydroxylase and 2'-glycosyltransferase. Also two genes involved in the biosynthesis of synechoxanthin, cruE and cruH were characterized. CruE is a β-ring desaturase/methyl transferase that forms aromatic χ-rings, CruH is a C-18-χ-ring hydroxylase. Combined these constitute six of the now twelve known carotenoid specific biosynthetic enzymes in Synechococcus sp. PCC 7002. These findings shed light on the synthesis of cyclic carotenoids and xanthophylls in cyanobacteria, and on the biosynthesis of carotenoids in general.