Background/Aim. The use of calcium channel blockers, especially nifedipine, causes gingival hyperplasia which leads to the destruction of the deeper periodontal tissues. During this process, inflammatory changes and the changes of colagen fibers occur. The aim of this study was to metrically compare the extent of proliferation of connective tissue in the deeper periodontal tissue in experimental animals regarding the dose and duration of nifedipine administration. Methods. The study involved 50 Wistar rats to which water solution of nifedipine was given in certain time intervals and doses. Before starting the experiment, i.e. before nifedipine administration, and in the defined time intervals, measuring of the morphology of gingival size was performed including the buccolingual and mesiodistal wideness and vertical altitude of the central interdental papilla. The measurement was performed by the use of a special graduated probe. Histometric analyses of the tissue samples were done on the sagital cross-sections in the direction from the top to the bottom of papilla on five levels. For the statistical analysis of the data, the established values to the extent of the most present changes were used. The mesiodistal and buccolingual diameters for the levels L2 and L3 were quantitively determined and compared. These values were compared to the vertical diameter of gingival growth determined before the onset of patohistologic analyses of the tissue samples. Results. At the beginning of the experiment, the volume of the lower incisive central papilla in the rats was 12 mm3. The central interdental papilla vertical altitude was 6.6 mm in rats which had received a lower dose of nifedipine, 8 mm in rats which had received a higher dose in the defined time intervals while the value for the control group was 3.8 mm. Conclusion. The obtained results showed that the administration of nifedipine led to the extensive gingival hyperplasia in the experimental animals. Gingival hyperplasia correlates with both the dose of nifedipine and the duration of its administration.