Examination of nearly a thousand books printed before 1500 has revealed indexes, some printed, some manuscript, in 83 of them, enabling some conclusions to be made on late medieval indexing policy and practice. The likelihood of indexing in particular subject areas; whether the index {or registrum or tabula) is explained; and the structure of the indexes, are among topics covered. The vagaries of primitive alphabetization are outlined, and an attempt is made to assess quality. Some of the indexers of these indexes are known by name. There is much worthy of study in medieval indexes, which are not merely of antiquarian interest. A list of the examined items is given.