HLA-A, B, C and DR typing was performed in 19 patients with sarcoidosis of acute onset. Besides bilateral hilar lymph node enlargement (BHL), ankle joint involvement was found in all and erythema nodosum in seven. HLA-B8 was present in 13 and HLA-DR3 in 17 of the 19 patients. The joint manifestations and the erythema nodosum subsided in all within three months. The BHL regressed completely in seventeen patients during a three year observation period. In two patients with an observation period of one year and less than six months, respectively, BHL were still visible. The strong association between the acute, prognostically beneficial manifestation of sarcoidosis and HLA-DR3 might partly be related to the presence of circulating immune complexes in acute sarcoidosis as well as to an immunogenetically determined handling of a postulated etiological antigen.