Gel-diffusion and the enzyme-linked immunosorbent assay (ELISA) were used to quantify and to identify the immunoglobulin class of teichoic acid antibodies in patients with chronic staphylococcal osteomyelitis and a wide variety of other infections. Teichoic acid antibodies were identified by gel-diffusion in 14 of 23 patients with staphylococcal endocarditis, six of 30 with staphylococcal bacteremia without endocarditis, four of 35 with staphylococcal skeletal infections, and one of 45 with nonstaphylococcal infections. None of the 20 patients with chronic staphylococcal osteomyelitis had positive gel-diffusion assays, even though many had had their infections for several years. The ELISA method was more sensitive than gel-diffusion in measuring teichoic acid antibodies, but was also much less specific. Teichoic acid antibodies were detected predominantly in the IgG fraction of serum. Our findings suggest that the presence and degree of antigenemia are more important than the duration of the staphylococcal infection in stimulating production of teichoic acid antibodies.