In an earlier study concerning patients with autoimmune diseases, a more reliable correlation of clinical disease activity was found with raised concentrations of the serum protein transcobalamin II than with several tests now in common use (complement factor C3, antinuclear antibody titer and antinative DNA binding capacity). These findings were subsequently confirmed in long-term observations over 1 to 3 years: the present paper discusses 5 of 7 investigated cases (2 with SLE, 2 with dermatomyositis of changing activity, and 1 with an erroneous diagnosis of SLE) in detail.