Background: Brucellosis, a zoonotic infection, was most widely diagnosed by the Brucella standard serum agglutination test (SAT). No previous publication has demonstrated a correlation between the degree of Brucella SAT agglutination positivity and the severity of brucellosis infection. Objective: To contribute to the clarification of the relationship between patelets and brucellosis. It is also aimed at evaluating the usefulness of the SAT titer as a measure of brucellosis severity. Material and Methods: We compared the control (n=60) and patients (n=96) groups in terms of mean platelet volume (MPV), C-reactive protein (CRP) and platelet values. Patients were grouped according to their degree of agglutination positivity titers and compared by means of CRP, MPV and platelet values. We also investigated the relationship among logarithmic values of MPV, platelet and CRP parameters for each group. Results: Although statistically meaningful difference was observed between control and patients group in terms of MPV and platelet value, there were no statistically significant differences observed among patients groups. The physiological negative correlation between MPV and platelet count was not encountered in group 2 and 3. Logarithmic values of CRP were not correlated with logarithmic values of MPV and platelet counts. Conclusion:The MPV could be a new parameter to evaluate hematologic abnormalities in patients with brucellosis. The SAT titer was not a useful measure for evaluation of the severity of brucellosis.