['Angiotensin-converting enzyme (ACE) has an important role in inactivation of bradykinin and tachykinins which known as powerful bronchoconstrictors. It has been demonstrated that an insertion (1)/deletion (D) genetic variations within the ACE gene greatly influence the plasma level of ACE.', 'The aim of the present study was to determine the frequencies of ACE D and I alleles and ACE DD, DI and II genotypes in asthmatic patients and controls with Iranian Azeri-Turkish origin and to compare the frequency of the ACE genotypes between asthmatic patients and controls.', 'We genotyped 212 healthy controls including 73 males and 138 females, as well as 62 patients with asthma, including 28 males and 34 females by PCR.', 'Of the 212 healthy controls: 1) the prevalence of DD, DI, and II genotypes were 83(39.151), 92(43.396) and 37(17.453), respectively. 2) the frequency (%) was 257(60.9)for D allele and 165(39.1 )for II allele. 3) D and II allele frequencies were 0.61 and 0.39 respectively. Of the 62 patients with asthma: 1) the prevalence of DD, II, and III genotypes were 17(27.42), 31(50) and 14(22.58), respectively. 2) the frequency (%) was 65(52.42)for D allele and 59(47.58 ) for II allele. 3) D and II allele frequencies were 0.52 and 0.48 respectively. Statistical analysis showed that studied groups (female + male patients group and female + male controls group) were in Hardy-Weinberg equilibrium. Our findings imply that II/D ratio was 0.61/0.39 in all controls and 0.6/0.4 in male or female controls. Significant differences were not found in the ACE genotype or allele frequencies between studied groups regarding all cases versus all controls, female cases versus female controls, male cases versus male controls.'] Is deletion allele of the ACE gene a risk factor for asthma predisposition?