This is a summary report of the vowel duration data that have been accumulated over the past several years. The data corpus analyzed to derive temporal controls of vowels consists mainly of three different readings by three different speakers, each about 10 to 20 min in duration. The rules cover the temporal behavior of vowels under many phonological conditions. The conditions include stressed and unstressed positions, prepausal and nonprepausal positions, word-final and non-word-final conditions, and monosyllabic and polysyllabic words. The influence of following consonants is discussed as well. Included also are conditions other than phonological ones, such as the effect of the prominence of words on their vowels, and the speed of reading. The duration rules derived from the data are intended for use in our speech synthesis-by-rule system from printed text. Subject Classification: 70.20, 70.70.