To facilitate gene finding and for the investigation of human molecular genetics on a genome scale, we present a comprehensive survey on various statistical features of human exons. We first show that human exons with flanking genomic DNA sequences can be classified into 12 mutually exclusive categories. This classification could serve as a standard for future studies so that direct comparisons of results can be made. A database for eight categories (related to human genes in which coding regions are split by introns) was built from GenBank release 87.0 and analyzed by a number of methods to characterize statistical features of these sequences that may serve as controls or regulatory signals for gene expression. The statistical information compiled includes profiles of signals for transcription, splicing and translation, various compositional statistics and size distributions. Further analyses reveal novel correlations and constraints among different splicing features across an internal exon that are consistent with the Exon Definition model. This information is fundamental for a quantitative view of human gene organization, and should be invaluable for individual scientists to design human molecular genetics experiments.