Whereas full, well-recorded fingerprints provide extensive detail for comparison, full prints are not always available. As a result, an important issue is the level of information needed to justify a conclusion regarding the identity of fingerprints. None of the previously proposed models for the quantitative assessment of fingerprint individuality incorporates the basic features of fingerprint comparison. The ridge structure is the most basic feature of the fingerprint. This structure and the resulting neighboring pairs of minutiae form the basis of a proposed method for describing fingerprint detail. A survey of 2,645 neighbor minutiae in 412 thumbprints shows that the distribution of minutiae around a centrally located minutia follow a gamma distribution. The observed parameters in male thumbprints of these adult males, whose prints were on file in a California criminalistics laboratory, were the basis of the proposed quantitative model. A comparison of the model with previous ones, a discussion of its limitations, figures showing details of numerous fingerprints, data tables, and 37 references are included. (Author abstract modified)