Two hundred serum specimens including 13 sera from patients with early Lyme borreliosis, 21 patients with late Lyme borreliosis, 15 rheumatoid factor positive sera, 31 sera from patients with syphilis and 84 sera from healthy controls were used to evaluate the following assays for the detection of antibodies to Borrelia burgdorferi: two in-house enzyme immunoassays (EIAs), two in-house immunofluorescent antibody assays (IFAs), a commercial haemagglutination assay (HA) (Diagast) and four commercial EIAs (Diagast, Dako, Diamedix, Whittaker Bioproducts). In early and late Lyme borreliosis sera sensitivity ranged from 8% to 62% and from 62% to 86% respectively. With the exception of the Dako EIA, which was signifcantly more sensitive in early Lyme borreliosis (62%) than the Diagast HA (8%) (p = 0.05), differences in sensitivity were not significant. In healthy controls the specificity was > or = 95% for all tests. Taking into account sensitivity, specificity, intra-test and inter-test precision, ease of performance and cost, the Dako EIA and Diamedix EIA were shown to be good alternatives to the in-house EIA and in-house IFA. Because of its low sensitivity in diagnosis of both early and late Lyme borreliosis, use of the Diagast HA should be discouraged.