Mental retardation (MR) is a typical feature of Langer-Giedion syndrome (LGS). Only 18 cases of LGS without MR have been reported. All of them either had normal karyotype or carried a deletion not exceeding the 8q24 band. Thus, it has been proposed that MR in LGS patients is associated with larger deletions. A patient with LGS and a large 8q23.2-q24.22 deletion but without MR is reported. This case suggests that there is not any particular gene which alone is responsible for MR in LGS patients, but it is the reduced expression of a large number of genes which predisposes to MR.