A new procedure was developed for isolation and immunochemical identification of amyloid proteins. This procedure involves extraction of amyloid proteins from tissues with aqueous acidic acetonitrile, their purification by HPLC and identification by ELISA. In this way the type of amyloid proteins was defined in amyloid-containing tissues obtained from 15 patients. The technique is simple, rapid and enables typing of amyloid proteins using only milligram amounts of tissue. This is in contrast to the conventional amyloid isolation and chemical identification technique which is laborious, time consuming and requires gram amounts of tissues. The procedure may enable the identification of the type of amyloid in biopsy specimens and thus help in evaluation of prognosis and determination of the therapeutic policy.