Prosodic information, such as word stress and speech rhythm, is important in language acquisition, and sensitivity to stress patterns is present from birth onwards. Exposure to prosodic properties of the native language occurs prenatally. Preterm birth and an associated lack of exposure to prosodic information are suspected to affect language acquisition in preterm infants. Fifty healthy very low birthweight (less than 1500g) preterm German infants (24 males, 26 females; mean gestational age [GA] 27.6 wks, range 26.4-29.9) and 103 comparison term infants (48 males, 55 females; mean GA 40 wks, range 39.4-40.8) were recruited. Prosodic discrimination performance was assessed using the head-turn preference paradigm, an objective behavioural psycholinguistic test for measuring orientation time (OT) to auditory stress patterns. Among matched preterm and term infants, preterm infants (n = 30) did not differentiate stress patterns at the corrected age of 4 or 6 months. In term infants (n = 30), the OT was longer towards the trochaic (stress on first syllable, characteristic for German) than the iambic (second syllable) stress patterns (11.64 vs 9.18s, p less than 0.001, and 11.02 vs 8.32s, p less than 0.001, at 4 and 6 mo respectively). Neurodevelopmental scores (Bayley Scales of Infant Development, 2nd edn) were not different from reference values in both groups of infants. Preterm birth and deficient early prosodic information affect prosodic processing during the first half year of life. (Contains 3 tables and 1 figure.)