Described is the experience from a single histocompatibility typing laboratory sampling, firstly, Australian patients with various immunopathic diseases and, secondly, subjects previously classified as "responders" or "non-responders" to various microbial antigens. The diseases considered included chronic active hepatitis (CAH) and various cirrhoses, "thyrogastric" autoimmune diseases, systemic lupus erythematosus (SLE), rheumatoid arthritis, dermatitis herpetiformis (DH) with intestinal villous atrophy, and multiple sclerosis (MS). The immune responses considered included those to flagellin, candidin, mumps, trichophyton, tuberculin and streptococcal enzymes. The HLA specificities particularly associated with disease included B8 (CAH, thyrotoxicosis SLE, DH, and miscellaneous immunopathic diseases) and B7 (thyrotoxicosis, SLE, DH, and MS). The same specificities were present in excess, although not impressively so, among responders to certain of the microbial antigens, i.e. B7 with high responders to flagellin and B8 (and A1) with responders to trichophyton.