The competitive ELISA test was compared with competitive RIA, complement fixation, and indirect fluorescent antibody test for the detection of antibody to varicella-zoster virus (VZV). ELISA and RIA were the most sensitive tests, being tenfold as sensitive as indirect immunofluorescence and 20 times as sensitive as complement fixation, which was surprisingly inadequate for detecting anti-VZV in sera from regular haemodialysis patients. The ELISA test was found to be the most suitable assay, employing a routine complement fixation test (CFT) grade viral antigen and not requiring radiolabelling and counting facilities, which are unavailable in most virology laboratories.