The difficulties that were encountered in making this selection of George Udny Yule's papers were of deciding what to exclude rather than what to include. It was with reluctance that we omitted Yule's pioneering work on pauperism (1895c, 1896a, b), which is still of methodological interest to sociologists. We were as sorry not to be able to include his unique paper on the logical consistence of class frequencies (1901), since its length would have made this volume too large for comfort. Many other of his famous contributions to statistical theory (e.g. (1922a) on the chi-squared test) have been excluded for the same reason. The twelve papers finally selected fall into three distinct groups.