Slovenian language is among the richest Slavic languages in view of the number of dialects. More than 40 dialects in seven dialect groups can be found on a territory of about 21,000 km2 and population of 2 million. Given the richness of influencing factors on the Standard Slovenian language we decided to undertake an acoustic analysis of its contemporary vowel system. Results on vowel formant frequencies and durations using the Kay Elemetrics Computerized Speech Lab are presented for the monophthongs uttered by educated speakers of Standard Slovenian. The emphasis of research reported in this paper is on a comparative analysis of durations of the Slovenian vowels. The measurements support the basic division of vowels into long stressed and short unstressed ones, while the further subdivision of stressed vowels into long and short only seems to be valid for one particular vowel, i.e., the open central vowel /a/.