A solid‐phase radioimmunoassay (RIA) has been developed for the detection of human rotavirus‐specific IgA, IgG, and IgM antibodies. Nebraska calf diarrhea virus grown in LLC‐MK2 cell cultures in the presence of trypsin was directly adsorbed onto polystyrene balls, and antibodies that attached to the virus‐coated balls were detected by subsequent binding of 125I‐labeled antibodies specific to human alpha, gamma or mu chains of human IgA, IgG, or IgM immunoglobulins. A total of 116 serum specimens from 58 adult patients were tested. Binding ratios between the positive and the negative serum varied between 5 and 15, occasionally being 20 or more in the IgA and IgG assays, but rarely exceeding 3 in the IgM assay. The RIA was found to be more sensitive in detecting antibodies to rotavirus than the complement fixation (CF) test, the RIA titers obtained being 50–100 times as high as the CF titers. The method described offers a possibility of evaluating the immune response to human rotavirus and of detecting recent infection. Copyright © 1978 Wiley‐Liss, Inc., A Wiley Company