Diameter growth of selected codominant and dominant beech individuals was measured using dendrometers. The measurements were performed repeatedly after each 14 days within the period between 1994-1997. The trees were situated on partial plots (PPs) with varying stocking (0.3, 0.5, 0.7, 0.9). Based on the analysis of the growth curves of the studied beech individuals it has been confirmed that the conversion to the per cent values relatively to the total annual amount enabled us to synchronise the curves of the individual trees. On the observed trees the diameter increment was generally formed from the first half of May up to the beginning (or even end) of September. In general, maximum amount of the increment in the individual years was created in June. In the individual years the trees under study were measured at the end of June, July and August, and were found to have created in average from 48 to 66%, 79-89% and 92-99% the total annual increment, respectively. From the variables observed at the PPs and on the individual trees it follows that the diameter increment amount was significantly influenced by the competition index. The value of the index was significantly dependent on the PPs stocking as well as on the initial diameters of the individual trees. At the same time the existence of near connection between the diameter increment values in two following years has been confirmed.