Background and Aim: Acute brucellosis among household members of Brucella patients has been reported. The aim of this study was to determine the effectiveness of active serological screening in detecting additional unrecognized cases among people who were in contact with patients suffering from acute brucellosis.Materials and Methods: This descriptive study was conducted among people who were in contact with Brucella patients (contact cases) in two provinces (Tehran and Lorestan) of Iran, between years 2005 to 2007. Five mL of venous blood samples were taken from Brucella patients (index cases) and contact cases and evaluated by using Brucella ELISA IgM, IgG, IgA assay kits.Results: 36 Index cases with the mean number of contact cases (4.5±2.5) with 117 contact cases [59 (50.5%) men, 58 (49.5%) women] were screened. Positive IgM, IgA, IgG ELISA titers were detected in 7 (6%), 25 (21.5%), 31 (26.5%) of contact cases, respectively. The seroprevalence rate was detected in 40 (34.2%) among contact cases. 38 (32.5%) of contact cases manifested various symptoms. Among 40 contact cases with positive seroprevalence, 14 (35%) cases had complaint, but among 77 contact cases with negative seroprevalence, 24 (31%) cases had complaint. There was not a significant correlation between positive seroprevalence with clinical complaint.Conclusion: The high seroprevalence rate (34.2%) and symptomatic individuals among contact cases (35%) in this study showed that the household members are not the single most important identifiable risk group and screening of other contact cases is necessary. Screening all contact cases provides an effective means for their early diagnosis.