In some countries, measurement of nuchal translucency (NT) is incorporated into national antenatal screening programmes to help detect pregnancies at increased risk of Down syndrome. Accurate measurement of the NT requires a specific technique. This article is an illustrated practical guide outlining the steps required for measuring the NT; it provides useful tips for improving operator technique and advises how to avoid common pitfalls. Although fetal nasal bone assessment does not currently form part of official Down syndrome screening programmes (in Australia or the UK), it is included here as debate about its usefulness continues.