A phoneme identification experiment manipulating closure duration was carried out to investigate perception of the word-medial voicing contrast by Dutch four-year-old, six-year-old, and 12-year-old children, and Dutch adults. Pretest results show that all children responded correctly to real-word minimal pairs differing in stop voicing. Subsequently, subjects were tested in an identification task ... [Show full abstract] using nonsense words, in which closure duration for labial and alveolar stops was manipulated through waveform editing. The two older age groups consistently distinguished voiced and voiceless stops. The younger children displayed a relatively high percentage of ambiguous responses, indicating that they had difficulties with the categorization of voiced and voiceless stops. Results are discussed in relation to adult perception, the perception-production relationship, and early infant research. It is argued that phoneme perception in children from the age of four evolves synchronously with their phoneme production, and that the perceptual processes develop gradually with age.