OBJECTIVE: Spinal muscular atrophy (SMA) is one of common autosomal recessive diseases and is characterized by degeneration of the anterior horn cells of the spinal cord. The reported prevalence is 1/10000 live births with a carrier rate of one in 50. It is important in genetic counseling to identify the carriers with one copy deletion for the survival motor neuron (SMN1) gene. However, the duplication of the SMA locus makes the detection of SMA carriers difficult. This study aimed to determine the potential of the quantitative PCR analysis in the identification of SMA carriers. METHODS: The SMN1 gene copy number was detected by real-time PCR with TaqMan technology in 109 SMA parents of affected children and 40 normal controls. RESULTS: The average copy numbers of SMN1 in the individuals with known one copy of the SMN1 gene and with the two copies were 0.777±0.035 (CV=4.5%) and 2.064±0.120 (CV= 5.8%) respectively. The average copy number of SMN1 in all of the parents with affected individuals was 0.798±0.108 (CV=13.5%), and that of normal controls was 2.106±0.18 (CV=8.5%). About 98% of SMA patients' parents carried 1 copy SMN1, and 95% of normal controls carried 2 copies. CONCLUSIONS: The gene copy numbers for SMN1 were one and two for SMA carriers and non-carriers, respectively. Our results suggested that the quantitative PCR analysis can distinguish the SMN1 deletion carriers from non-carriers.