Motivation: What forces maintain transposable elements (TEs) in genomes and populations is one of the main questions to understand the dynamics of these elements, but the exact nature of these forces is still a matter of speculation. To test theoretical models of TE population dynamics, we need many data on the genomic distributions of various elements. These data are now accumulating for the species Drosophila melanogaster, but they are scattered in the literature. Results: The knowledge base DROSOPOSON thus brings together: (1) data available on Drosophila chromosomal localizations of TE insertions and on features of the polytene chromosomes (DNA content, recombination rate, breakpoints, etc.); (2) statistical methods aimed at analysing the distribution of the TE insertions along the chromosomes. In this paper, we present the structure of the base, the data and the statistical methods. Theoretical models of containment of TE copy number in Drosophila can thus be tested. Availability: All the program sources, knowledge base schemes and data are available through anonymous ftp at biom3.univ-lyonl.fr (directory: pub/drosoposon). Contact: E-mail: [email protected]