OBJECTIVE To assess the value of quantitative fluorescence PCR (QF-PCR) for the prenatal diagnosis of common fetal chromosomal aneuploidies. METHODS A total of 2436 amniotic fluid samples were collected at 18 to 22 gestational weeks. Multiplex QF-PCR was performed with fluorescence-labeled primers specific for 32 polymorphic short tandem repeat (STR) sites on chromosomes 21, 18, 13, X and Y. The PCR products were assayed by capillary electrophoresis. All samples were also assayed by karyotyping. RESULTS Seventy-six (3.12%) samples were diagnosed as chromosomal aneuploidies by QF-PCR, among which 51 were trisomy 21, 12 were trisomy 18, 2 were trisomy 13, and 1 was triploidy. The results were all consistent with those of karyotyping. Ten samples were suspected as sex chromosomal aneuploidies, among which 9 were confirmed, except for 1 case with X structural abnormality. In addition, karyotyping has diagnosed 24 (0.99%) cases of structural abnormalities, only one of which was suspected by QF-PCR with partial abnormal STR results. Two (0.08%) samples were found to be mosaic by karyotyping, one of which was suggested by QF-PCR with cut-off ratios of STR markers. CONCLUSION QF-PCR is reliable for the diagnosis of numerical abnormalities of chromosomes 21, 18, 13, X and Y. The method can serve as an effective technique for rapid prenatal screening of common chromosome aneuploidies in fetus.