Mannan-binding lectin (MBL) is perhaps the best known of the collectins, a subfamily of C-type lectins possessing an additional collagen-like domain. MBL is thought to be an important component of innate immunity. Since the discovery, around 15 years ago, that MBL was identical to a factor responsible for the opsonization of baker's yeast in vitro, a large number of disease-association studies have been conducted. Most of these investigations support the view that MBL can influence susceptibility to, or affect the course of, many diseases. These include bacterial infections, rheumatoid arthritis, cystic fibrosis and recurrent miscarriage. This meeting was arranged to bring together scientists and clinicians to review the clinical significance of MBL, and to consider the most appropriate target disorders for MBL-replacement therapy.