The distribution of Goodpasture antigen (GA) was studied in a range of human tissues using indirect immunofluorescence and immunoperoxidase techniques. Frozen sections were stained using (1) a mouse monoclonal antibody (P1) raised against the autoantigenic component of human glomerular basement membrane, (2) autoantibodies eluted from the kidneys of patients with Goodpasture's syndrome, (3) antibodies eluted from the kidneys of a sheep with Steblay nephritis, and (4) mouse monoclonal and guinea pig polyclonal antibodies to human type IV collagen. The same pattern of staining was demonstrated using the eluted antibodies and monoclonal antibody P1. The presence of GA was confirmed in the lung and choroid plexus. GA was also detected in basement membranes at a number of previously unreported sites in the eye, thyroid, pituitary, adrenal, breast, and liver. GA was absent from other sites at which type IV collagen could be demonstrated. Direct immunofluorescence studies of tissue from a patient with Goodpasture's syndrome revealed deposition of IgG in the choroid plexus and eye, as well as in the kidney and lung.