The effectiveness of vowel normalization methods has been suggested to be language-dependent. Six such methods have been used on Czech vowels to see which of them would lead to the best results in follow-up discriminant analyses while preserving the linguistically informative detail. The discriminant analyses had lower success rates for read continuous texts with multiple tokens from 75 speakers than for the carefully-pronounced monosyllables used previously by other authors, suggesting that the results might also be materialdependent. On the other hand, our variable data offered additional insights into sources of contextual variation and allowed us to identify the so-called enhancing contexts in which identity of a vowel is best preserved.