There is a significant difficulty in discriminating vowels sung at extremely high fundamental frequencies, especially, when the fundamental frequency (F0) produced is above the region where the first vowel formant (F1) would normally occur. Apart from the difficulties involved in discriminating vowels, aspects of phonology might be expected to contribute to problems of intelligibility. Can such vowels be correctly identified and, if so, does context provide the necessary information or acoustical elements are also operative? The paper studies the perception of sung vowels in order to get insight on the issue of singing intelligibility. A perceptual study on the intelligibility of the Russian vowels was carried out. 49 subjects underwent perceptual tests which were aimed at identifying sung vowels. Classification of the confusions showed that incorrectly identified vowels tend to be confused with [a]. The acoustic analysis of the material was also carried out. The results of perception and acoustic analysis are compared and discussed.