Thirty-seven unrelated Iranian CF families were screened for the presence of seven common mutations (DeltaF508, G542X, W1282X, G551D, N1303K, 1717-1G-->A, and 621-1G-->T) using ARMS PCR and exons 4 and 7 of the CFTR gene by SSCP method. This study resulted in the identification of 26.8 per cent of all CF alleles: DeltaF508 (16.2 per cent), W1282X (4 per cent), G542X (2.7 per cent), R117H (1.3 per cent), R347H (1.3 per cent), and A120T (1.3 per cent) mutations were detected. To the best of our knowledge, it is the first report of an Asian subject carrying the A120T mutation. Our findings suggest heterogeneity in the Iranian population, stressing the need to draw attention to sequence analysis in order to find population-specific mutations.