A particular aspect of syllable structure, length of syllable margins, was investigated with the aid of a Markov chain model. The model represented explicitly the dynamic relationship between types of syllable structure and the historical processes that affect them. It is proposed that the regularities concerning syllable types (universality of CV syllables, etc.) are best understood and explained if they are assumed to be nondeterministic--referring to the relative frequency of occurrence rather than occurrence vs. nonoccurrence. A number of specific generalizations about other aspects of syllable structure are also proposed on the basis of the data and the analysis. (Author)