Fibrillar collagens are ubiquitous proteins essential for the structural integrity of bones, skin, blood vessels, and other tissues. Mutations in collagen genes result in disorders including osteogenesis imperfecta, chondrodysplasias, and Ehlers-Danlos syndromes, but the molecular basis for the heterogeneity of clinical phenotypes is not well understood. A more complete understanding of the relationship between sequence and phenotype requires synthesis of multiple facets of collagen structure and function. To facilitate such an analysis, we developed COLdb, a freely available database integrating collagen biological and physicochemical properties with known variants. A Web-based, interactive, graphical user interface displays the data as annotations on the collagen protein sequences. Collagen gene-level data are provided as custom tracks for display in the UCSC genome browser. COLdb currently includes 35,582 data points spanning collagen types I, II, and III, and, importantly, users can add their own data to the display. The database is the first comprehensive integration of disparate functional information on the three major fibrillar collagens, and the first electronic collection of mutations in the COL2A1 gene.