The aim of this prospective study was to assess the repeatability of measurement of fetal nuchal translucency thickness at 10-14 weeks' gestation. The nuchal translucency was measured by two of four operators in 200 pregnant women attending the Harris Birthright Research Centre for Fetal Medicine at 10-14 weeks' gestation. To assess repeatability of different components of variability, six measurements of nuchal translucency were made on each fetus, with a total of 1200 measurements. The data of this study demonstrate that 95% of the time the intraobserver, interobserver and caliper placement repeatability of measuring fetal nuchal translucency were less than 0.54 mm, 0.62 mm and 0.58 mm, respectively. In addition, the repeatability was unrelated to the size of the nuchal translucency. The findings of this study demonstrate that, when the nuchal translucency thickness is measured by well-trained operators, the measurement is highly reproducible.