Objectives: To determine the sensitivity and specificity of middle cerebral artery peak systolic velocity (MCA-PSV) in mid-pregnancy for the identification of homozygous α-thalassemia-1 (hemoglobin (Hb) Bart's disease) in fetuses at risk of the disease. Methods: A total of 88 pregnancies (91 fetuses) at risk of Hb Bart's disease and undergoing MCA-PSV measurement before cordocentesis at 18-22 weeks of gestation were recruited into the study. Definitive diagnosis was made using the gold standard technique of Hb typing by high-performance liquid chromatography. Results: The mean ± SD age of the 88 pregnant women recruited into the study was 28.3 ± 5.7 years, the gestational age was 18.8 ± 1.1 weeks and the incidence of Hb Bart's disease was 22% (20 fetuses). Using MCA-PSV above 1.5 multiples of the median as a cut-off point, the sensitivity of MCA-PSV for detecting affected fetuses was 85% (17/20 cases), with a specificity of 100%, and positive and negative predictive values of 100% and 95.9% respectively. Three of 20 fetuses with Hb Bart's disease had normal MCA-PSV. Conclusions: MCA-PSV assessment in mid-pregnancy is a useful method for identifying Hb Bart's disease with high sensitivity and specificity among fetuses at risk, and may allow avoidance of unnecessary cordocentesis in some cases. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.