Objective. To study the relationship between antibodies that recognize human retroviral proteins and the presence of clinical features and ribonucleoprotein antibodies in patients with autoimmune connective tissue diseases (CTDs).Methods. Antibodies against native human immunodeficiency virus type 1 (HIV-1) and human T cell leukemiahymphoma virus type I, recombinant HIV-1 Nef protein, and ribonucleoprotein antigens were determined by immunoblot of sera from 65 prospectively studied patients with definite ur suspected CTDs of autoimmune type.Results. Antibodies to retroviral proteins (ARP), most frequently to HIV Gag proteins p55 and p24, were found in 64% of 22 patients with systemic lupus erythematosus (SLE), in 63% of 8 patients with discoid LE From the