During 2000 we made certain research into prevalence of the patients with an acute pneumonia at rural as well as town inhabitants of West Herzegovina (FBiH) within the population of 29,000 inhabitants 236 cases (0.81%) of acute pneumonia with specific clinical-lab results and the x-ray of the lungs, has been diaponesed in general population. Mortality was 2%. For the differentiation of bacterial from atypical pneumonia it was of very importance CRP (reactance of acute phase which was raised from the first day of pneumonia attack), the concentration of leucocytes with-in differential blood count. The average values of erythrocute sedimentation at the first checkup of the patients i.e. at the beginning of bacterial and atypical pneumonia were almost the same. But after a week the values were divergent and a little big higher at the patients suffered from bacterial pneumonia.