The aim of the study was to determine the IgG antibody response to spotted fever group Rickettsia (SFGR) R. conorii and R. slovaca, and its specificity and sensitivity in patients with DEBONEL/TIBOLA. A prospective study of 31 patients with DEBONEL was carried out from January 2001 to May 2004. The SFGR serology testing (IgG IFA) for the diagnosis of DEBONEL/TIBOLA showed 61% sensitivity and 100% specificity. The R. slovaca antigen allowed the diagnoses in 18 of the 31 patients (58%), and 17 patients (55%) were diagnosed with this disease using R. conorii antigen. Therefore, using R. slovaca as antigen did not improve the sensitivity of the assay.