Some northern varieties of Basque possess three series of plosive or oral stop consonants: voiced /b d g/, voiceless unaspirated /p t k/, and voiceless aspirated /ph th kh/. Among the languages of Europe, Basque seems to be unique in presenting this three-way opposition (although a similar contrast was found in Ancient Greek and it is not unusual in other parts of the world). For this reason it is important to document this phonological contrast; even more so since the dialects that maintain this contrast (which is believed to have been much more general in Basque in the past) appear to be in serious danger of extinction. For the study reported here, data were collected from 4 male speakers of Zuberoan or Souletin, the easternmost Basque dialect using a high-quality digital recorder. The data were then analyzed using a computerized speech analysis sytem (Ahotsa, developed by I. Hernaez). Voice Onset Time (VOT) measurements were taken, since this acoustic dimension has been proven to have an excellent correlation with voicing and aspiration in many other languages. The results agree with those that have been reported for other languages with a similar three-way contrast. In utterance-initial position, /b d g/ are prevoiced (negative VOT), /p t k/ have present a short lag (VOT around 20 ms) and the aspirated /ph th kh/ present a much longer lag (average VOT between 60 and 80 ms depending on the place of articulation of the consonant).