The aim of this research was to evaluate the clinical course of chronic apical periodontitis (CAP), treated only endodontically, without periapical medication. Chronic apical periodontitis cases of pulpal origin were used as a material and treated endodontically as individual clinical cases. Clinical and statistical procedures were applied. The percentage of efficient or non-efficient cases was evaluated on the basis of radiographic comparison of treated CAP immediately after obturation, and six months later. Influences of various factors on therapy effect were analysed: radiographic condition and type of periapical lesions, apical level of canal obturation, group of teeth and jaws as well as age. Radiographic conditions were assessed as status quo, improvement or deterioration. Final results were: 67.3% of improvement, 27.2% of status quo and 5.5% deterioration.