Background: The aim of the study was to assess the anaerobic threshold (lactate threshold LT) changes during winter and summer preparation period in soccer premier league and first division players. It was assumed that the index value varies depending on the stage of a one-year training cycle.Material/Methods: Tests were conducted on the premier league and first division soccer players. Physical capacity tests were carried out at the beginning and at the end of the winter and summer preparation period. The tests covered 3 years: 2008 - 2010. Subjects performed an incremental running test according to Jastrzębski's method. The most important data obtained from this test are: running speed (V/LT) and heart rate (HR/LT) at LT.Results: At the beginning of summer preparations the players' speed corresponding to LT reached the value of 3.69 m/s ± 0.31 m/s, while at the end of this period it increased to 3.86 m/s ± 0.29 m/s. During the winter preparatory season the values of this index were 3.81 m/s ± 0.3 m/s and 3.80 m/s ± 0.21 m/s, respectively.Conclusions: Tested subjects showed lower values of running speed at LT level at the beginning of the summer preparatory season than at its end. At the final stage of the winter preparatory season HR values at LT were significantly lower than at the initial stage of this period.