In order to understand insertion/delation (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene in pilots,and to explore the relationship between ACE gene I/D polymorphism and the performance of the pilots, the polymerase chain reaction (PCR) was used to determine the genotypes for an I/D polymorphism in intron 16 of the ACE gene in 118 pilots and 96 healthy subjects as controls. The result showed that the I/D polymorphism in intron 16 of the ACE gene was categorized into three genotypes: two deletion alleles (genotype DD), heterozygous alleles (genotype ID), and two insertion alleles (genotype II). The genotype II and I allele frequency were significantly higher in pilots (44.07% and 0.65) than that in healthy subjects (31.25% and 0.52). It is suggested that I gene of ACE may play a role in performance of the pilots.