Two groups of pupils from special tract learning schools were randomly selected for this study. The first group (55 pupils) fulfilled the World Federation of Neurology (WFN) definition of developmental dyslexia (DD). The second group (retarded readers, RR) included 20 pupils with IQs between 80 and 90. A group of normal readers was randomly selected from the 5 school grades as a control group. This study showed that the performance IQ of the DD group was not only higher than the verbal IQ, but the DD group also had superior performance IQ compared to normal readers. In the arithmetic achievement test, both DD and RR groups had nearly similar total scores, which were significantly lower than that of the control group. None of the arithmetic subtests could differentiate between DD and RR groups. In linguistic achievement tests, only spontaneous writing and oral spelling could differentiate subjects with DD from the RR group.