Abstract: Scots pine saplings were examined in some clear-cut sites in northern Finland. The length of the saplings, the number of annual needle crops and the mycorrhizal infection percentage were recorded in saplings grown in ploughed and unploughed sites in order to reveal 1) the effect of ploughing on mycorrhiza formation and 2) the effect of possible disturbances in mycorrhiza formation on the growth of saplings. The mycorrhizal infection percentage was significantly lower in the double humus layer at ploughed sites than in the undisturbed humus layer at unploughed sites. The mycorrhizal infection percentage showed a significant positive correlation with the length of the saplings and the number of annual needle crops. In injured saplings, in which the length and number of annual needle crops were lowest, mycorrhiza formation was also poorest.