Diagnosis of Rickettsia prowazekii forms at the final stage of its elimination. 30 cases of petechial typhus occurred in Russian Federation during the period from 1973 to 1996 were subjected to retrospective analysis. On the base of this analysis the false registration of disease "epidemic" form was revealed. Indeed it appeared to be the recurrences, i.e. the Brill's disease. The authors propose to use the table of differential diagnostic signs of both forms of Rickettsia prowazekii based on their clinical-and-epidemiological special features. It will help to avoid the false reports.