This paper presents a corpus-based study on prolongations in spontaneous Mandarin. Prolongations are mainly produced for hesitation, but also for emphasizing a discourse focus and signalling an explicit feedback. 786 prolongation occurrences are investigated in terms of the position, the part of speech and the segment and tone types. Prolongations are often found in word-final, phrase-final and utterance-medial positions. It is more likely to prolong in function words than in content words. However, in the case of monosyllabic words prolongations are more frequently found in function words, but in the remaining cases prolongations are more likely to be found in content words. Prolongations in transitive verbs, adverbs, nouns and particles show particularly high rates, while prolongations in intransitive verbs and aspectual adverbs are really rare. Especially, there is no prolonged adjective. Consonants are rarely prolonged in Mandarin and no particular effect is found for lexical tones.