The authors for the paper titled Positive association of the DIO2 (deiodianase type 2) gene with mental retardation in the iodine-deficient areas of china (J Med Genet 2004:41;585–590) have identified an error within their abstract. The second line from the results section should read: Particularly with rs255012, CC genotype frequency was significantly higher in MR cases than in controls (chi squared = 9.18, p = 0.00246). The author apologises for this mistake.