Pinus brutia (Ten.) is affected by various biotic and abiotic factors during its lifetime. Insect damage undoubtedly is the most important biotic factor for the tree. The European pine sawfly (EPS), Neodiprion sertifer (Geoff., 1785) (Hymenoptera: Diprionidae), eats the needles of P. brutia trees and damages their assimilation organs. In this study, as a result of leaf eating of EPS on the trees of young P. brutia; its effect on increment of diameter, height and volume and growth loss was studied from 2000 to 2004. For this purpose, three different pure young P. brutia generations in the districts of Aziziye, Burdur were chosen as the study area. EPS has caused an epidemic which continued for 5 years in the seedlings in that young generations. In the 5 aged young P. brutia generations, 45 non-infested and 45 infested groups were chosen and cut in three different areas. At the choosen seedlings stem analysis was made to compare the increment and growth of infested and non-infested groups. Discs for stem analysis were taken from 0.0 m and each 0.25 m of the seedlings which were cut. Annual rings in the discs were measured with the sensitivity of 0.01 and diameter, height and volume development were set for each sample seedling according to age. In the sample seedling which were in non-infested and infested groups, annual increments were compared with ANOVA Statistical Test. In the sample seedling which were in the non-infested and infested groups; diameter (F(1;88)=39.415***), height (F(1;88)=50.212***) and volume (F(1;88)=58.378***) growths were statistically different. Substantial decreases were identified in the growth of diameter, height and volume in the seedling which were in the non-infested group. These decreases on average were 39%, 28% and 71% successively.