Syllable structure in Piro, an Arawakan language spoken in Eastern Peru, exhibits properties that are of considerable interest. First, Piro allows three-consonant clusters in the syllabic onset (Matteson 1965) but a vowel-deletion rule is blocked to avoid such clusters, which makes it difficult to simply attribute the blocking to well-formedness constraints on syllable structure (cf. Kisseberth 1970a, b). Second, the onset consonant clusters are not governed by the Sonority Sequencing Principle (Selkirk 1984a, Clements 1990). The fact that all consonants except the prevocalic ones are described by Matteson (1965) as syllabic seems to obviate the need to posit complex onsets. However, these syllabic consonants do not participate in any phonological rules, including word stress and phrase-level rhythmic rules. If they are considered extrasyllabic throughout the phonology, they become exceptions to our general conceptions of extra-prosodicity, stray erasure and prosodic licensing (Itô 1986, 1989), since numerous such extrasyllabic consonants are not at the peripheral position of a well-defined domain but persist to be present throughout the derivation. Third, loss of an onset or unsyllabified consonant can lead to compensatory lengthening (henceforth CL), contradicting the moraic conservation account of CL (Hock 1986, Hayes 1989). Fourth, as Piro has no underlying long segments nor evidence for a heavy closed syllable, it becomes a counterexample to the typological prediction that CL occurs only in languages that have a pre-existing vowel-length contrast (de Chene & Anderson 1979) or syllable-weight contrast (Hayes 1989).