A method for rapid simultaneous determination of multiple autoantibodies in sera has been developed. 42 different antigens were coated onto a nitrocellulose membrane in a miniblotter apparatus with 42 lanes. The membrane was also coated with different concentrations of human IgG to create a standard curve. The blotting apparatus after coating, blocking and washing was turned 90 degrees so that all lanes crossed the antigen coated lanes. Thereafter, 42 sera were incubated with the antigens. After this stage the membrane was treated as in the usual dot-blot procedure. After incubation with alkaline phosphatase labelled anti-human IgG, staining and drying of the membrane, the staining intensity of individual lanes was scanned into a data file and analyzed by computer. By this method it was possible in 4 h to examine 42 sera for autoantibodies against 42 antigens, i.e., more than 1600 tests. Furthermore, the amount of antibody could be semi-quantified, using the IgG standards. The method should be useful for rapid screening of autoantibodies in a routine laboratory.