Genetics. In the article “The unique hetero-oligomeric nature of the subunits in the catalytic cooperativity of the yeast Cct chaperonin complex” by Paul Lin and Fred Sherman, which appeared in number 20, September 30, 1997, of Proc. Natl. Acad. Sci. USA (94, 10780–10785), the authors request that the following corrections be noted. On page 10782 in Table 1, the values for the cct1-5 × cct1-1, cct1-5 × cct1-2, and cct1-5 × cct1-3 crosses should all be 6. Lines 4–6 of the legend of Table 1 should read “0–6 denotes the relative growth of the strains, where 0 denotes no growth, and 6 denotes normal or near normal growth.” We apologize for these errors.