Fragile X syndrome is an important disease of hereditary mental retardation. Its prevalence in the Chinese population is not clear. We amplified FMR1 CGG repeats from male newborns' blood spots. Approximately 45% of the males had 28 CGG repeats and another 19% had 29 repeats. Besides this major peak, there was a second peak at 34 and 35 repeats. From the 1000 males studied, 3 were found to have repeat numbers in the high borderline range (each with 50, 52 and 53 repeats). This result provides a low but significant risk of fragile X syndrome in the Chinese population.