The invention relates to factor D inhibitors, which bind to factor D and block the functional activity of factor D in complement activation. The inhibitors include antibody molecules, as well as homologues, analogues and modified or derived forms thereof, including immunoglobulin fragments like Fab, F(ab)₂ and Fv, small molecules, including peptides, oligonucleotides, peptidomimetics and organic compounds. A monoclonal antibody which bound to factor D and blocked its ability to activate complement was generated and designated 166-32. The hybridoma producing this antibody was deposited at the American Type Culture Collection, 10801 University Blvd., Manassas, Va. 20110-2209, under Accession Number HB-12476.