Abstract Serum samples were taken during the first 3 weeks and I year after discharge from hospital of 16 patients with burns covering more than 35 per cent of the body surface area. The sera were tested for the presence of antinuclear, antimitochondrial, anti smooth muscle, anti brush border and anti gastric parietal cell autoantibodies using the technique of indirect immunofluorescence. Compared with measurements for the same autoantibodies, in sera from 25 healthy blood donors, the burned patients' sera showed the presence of anti smooth muscle autoantibodies in 81·2 per cent, anti brush border autoantibodies in 56·2 per cent, antimitochondrial autoantibodies in 31·2 per cent and antinuclear autoantibodies in 12·5 per cent of the sera. Autoantibodies to gastric parietal cells were not detected. A correlation was noted between the presence of antimitochondrial autoantibodies and alterations in liver function. In contrast, no correlations were found between the raised levels of the various autoantibodies and resuscitative fluid or antibiotic therapy, intercurrent infections, serum immunoglobulin levels, surgical treatment or the duration of stay in hospital. The high titre of autoantibodies to anti smooth muscle could have arisen from tissue protein degradation associated with the raised requirements for energy by the hypermctabolic patients.