In this report we present the sequences of four new cct chaperonin genes from the nematode Caenorhabditis elegans. The four genes, cct-2, cct-4, cct-5, and cct-6 are orthologs of the mouse chaperonin genes Cctb, Cctd, Ccte, and Cctz, sharing 66%, 63%, 68%, and 67% deduced amino acid sequence identity, respectively. The C. elegans multigene family includes these four genes as well as cct-1 (tcp-1), and displays 23-35% pairwise predicted amino acid sequence identity between members, and 31-35% identity to the closely related archaebacterial chaperonin TF55. The five C. elegans cct genes are expressed in all life stages (egg, four larval stages, and adult). Members of the multigene family occur as a loosely associated group of three genes on chromosome II, and two widely separated genes on chromosome III. The predicted secondary structures of all five C. elegans CCT deduced protein sequences are nearly identical. Moreover, all chaperonins examined had comparable predicted secondary structures. Algorithmic predictions of the secondary structures of GroEL, Hsp60, and Rubisco subunit-binding protein (RuBP) are almost identical, and are very similar to the known GroEL secondary structure. The CCT/TF55 family predicted secondary structures are essentially identical to each other and are also related to GroEL, Hsp60, and RuBP. The most notable difference between the CCT/TF55 and the GroEL/Hsp60/RuBP families is in the presumed polypeptide binding domain.