\Prose rhythm" is a widely observed but scarcely quanti ed phenomenon. We describe an information-theoretic model for measuring the regularity of lexical stress in English texts, and use it in combination with trigram language models to demonstrate a relationship between the probability of word sequences in English and the amount of rhythm present in them. We nd that the stream of lexical stress in text from the Wall Street Journal has an entropy rate of less than 0.75 bits per syllable for commonsentences. We observe that the average number of syllables per word is greater for rarer word sequences, and to normalize for this e ect we run control experiments to show that the choice of word order contributes signi cantly to stress regularity, and increasingly with lexical probability.