Abstract Background:  a-thalassemia trait is frequently encountered in Saudi Arabia with a large diversity and geographical variability in the underlying genotypes. Aim of Study: To characterize the molecular spectrum of a-thalassemia in the western province of Saudi Arabia in some Saudi patients suspected of a  thalassemia carrier or diagnosed with Hb H disease to determine if there is the significance of premarital genetic testing for a  thalassemia in a couple suspected with a  thalassemia trait. Patients and Methods: This study included 39 patients, 34 patients with suspected a  thalassemia trait and 5 patients diagnosed with Hb H disease. Results: Thirteen patients 33.3% are heterozygous for + thalassemia having the genotype --3.7/ and 14 patients 35.9% are homozygotes for 0 having the genotype -3.7/-a3.7 and, one patient with --MED /aa, one with --SEA /aa, and one PA-1 / and the 5 patients with HGB H disease 12.8%, one patient has a genotype of --SEA/-3.7, one with - -MED/-3.7 Mediterranean thalassemia ( --MED) with 3.7 kb heterozygous deletion, and 2 patients with genotype aPA-1 /aPA-1 Words: a thalassemia – Hb H disease – Saudi Arabia. mozygous mutation Poly A(A->G). There was one case with negative molecular screening for α-thalassemia. Conclusion: The -α3.7 was the most common mutation among patients with α-thalassemia forming 78.9% ofall deletions. The premarital genetic diagnosis of α-thalassemia is not recommended as -α3.7 deletion is not risk for hydrops fetalis but should be considered in families with a history of HGB H disease or hydrops fetalis.