Background: Sets of polymerase chain reaction (PCR) primers were used that make it possible to study subtypes of the most prevalent mutations that cause alpha-thalassemia (-alpha3.7 deletions). These primers (Dev and C3, Dev and C9c) can be used in PCR to amplify regions that are characteristic of the three - alpha3.7 deletion subtypes (alpha3.7i, alpha3.7ii, alpha3.7iii). These subtypes are important because the type of alpha-chain deletion can affect the level of alpha-globin production. Methods and Results: The PCR products were screened using automated high-resolution electrophoresis on a DNA sequencer. Subtypes were then identified by automated DNA sequencing. During the screening for subtypes with high-resolution fragment analysis, new fragments were detected that were slightly different from the expected size. DNA sequencing of these fragments demonstrated the presence of three mutations that had not been described or fully characterized before. Conclusions: High-resolution fragment analysis is a convenient way to detect alpha-thalassemia subtypes, and DNA sequencing of silent mutations can lead to a better understanding of the cause of these mutations.