The clinical utility of two complementary tests for brucellosis, the Brucella IgM and IgG flow assays, was evaluated in a hospital in eastern Turkey. The results show that the flow assays are convenient diagnostic tests for use in endemic areas. A positive result in the flow assays was obtained in 91% and 97% of the admission sera from adult and pediatric patients with brucellosis, respectively, and the sensitivity at admission was 100% for culture-confirmed brucellosis. The assay system performed equally well in diagnosing patients at different stages of illness including patients with acute, subacute, or chronic disease and with relapse. The results of the flow assays correlated well with those of a serum agglutination test at a cut-off greater than or equal to1:160. The agreement was 92%. Application of the flow assays on serum samples collected during a village survey for brucellosis after an outbreak demonstrated their diagnostic potential as field tests.