A total of 176 human fecal specimens were examined for the presence of rotavirus using four different assays: a monoclonal antibody enzyme immunoassay; the original polyclonal antibody enzyme immunoassay marketed by Abbott Laboratories, Chicago, IL (Rotazyme I); a modification of this assay which is now commercially available (Rotazyme II); and a latex agglutination test (Rotalex) recently introduced by Medical Technology Corporation, Somerset, NJ. In addition, selected specimens were examined for the presence of rotavirus by electron microscopy, immune electron microscopy and by RNA gel electrophoresis. Forty specimens were positive using the monoclonal antibody enzyme immunoassay; 136 were negative. Using the results obtained with the procedure as the reference standard, the sensitivities of the Rotazyme I, Rotazyme II and Rotalex tests were 97.4, 100, and 81.6% respectively. The specificities of these three procedures were 88.8, 83.9, and 100%, respectively.