The main acoustic features of vowels in Karitiana, a language of the Tupi stock spoken in Brazil are examined. This language has 5 vowel qualities [i,e,a,o,l/] which can be oral (short and long) and nasal (short and long). This vowel system has no high back vowel [u]. The main characteristics are that short oral vowels have a wider distribution than long oral vowels; nasal vowels are centralized when compared to oral vowels; length measurements show that central vowels are very short; whatever their quality short nasal vowels have similar length; the difference between short and long nasals is less than in the oral dimension. The dynamic characteristics of nasal vowels where there is a characteristic rising movement of F2 are also examined. Finally a perception test was carried out to understand how Karitiana vowels are perceived by native speakers. The test used a set of 58 synthetic stimuli which covers the vowel space. The main results show that speakers easily recognize peripheric vowels while central vowels are less salient. Karitiana speakers did not identify any stimuli in the area of the high back vowel.