The sonographic assessment of cervical length is a well established method for pregnant women with an increased risk of preterm delivery. Even in asymptomatic patients, but with specific risks for preterm delivery, a selected screening has become successful. Up to now a screening in the general population is not recommended, as the sensitivity and specificity in this group are quite low. Therapeutic interventions or preventions are more efficient and under objective criteria with the use of cervical length measurement. The further development will be a combination of sonographic, biophysical and biochemical markers. This includes the multiple causes for preterm delivery and pronounces the central role of sonographic assessment of the zervix. For induction of labour at term the results of cervical length assessment are promising. The interval between priming and delivery and the success rate for a vaginal delivery within 24 hours can be predicted more precisely. It optimises the organisation of a busy delivery unit and motivates the pregnant woman.