We have detected five 99.4 kb deletions in chromosome Xq28 affecting MECP2 associated with mild manifestations of classic RTT and five deletions encompassing MECP2 spanning 502.428 kb (three cases), 539.545 kb (one case) and 877.444 kb (one case) associated with mild atypical RTT. The gene discussed is MECP2; the disease is Rett syndrome.