Background: Poor knowledge about Fragile X syndrome (FXS) may be a major barrier to early diagnosis that could improve quality of life and prognosis especially in the developing countries. Aim: The aim of this study was to evaluate simple and reproducible method for premutation detection in females of fragile X families for the first time in Egypt. Subjects and Methods: We have developed a rapid modified polymerase chain reaction (PCR)-based screening tool for expanded Fragile X mental retardation 1 (FMR1) alleles. This method utilizes betaine as additive to facilitate FMR 1 gene amplification. We screened fifty three males, thirty two first-degree females; twenty normal healthy controls in addition to six reference samples. Results: Simple PCR method showed 16 males with abnormal CGG repeats, where 10 of their mothers and four sisters had FMR 1 premutation. Consanguineous marriage was present in 66.6% percent of the studied families. Studying the correlation between genotype and clinical manifestations showed premature ovarian failure in 40% and learning disability in 50% of the studied female carriers. Conclusion: FXS has to be ruled out in families with consanguineous parents, before assuming that familial mental retardation is due to autosomal recessive gene defects. Early carrier detection may reduce the number of affected children. In conclusion, more studies are still needed of much larger sample size with known allele sizes in order to guarantee the accuracy of the method used.