In this study, the regression equation modelling diameter increment of single tree by stand age and stand density degree was developed for stands of Brutian pine (Pinus brutia Ten.) located in Aglasun Forest Enterprise. The data were obtained from 54 sample plots with its stand age (Age=32-37) and stand density degree (SD=0.771-1.416). The coefficient of determination (R2) standart error (Se) of this regression model are 0.5845 and 0.802 mm/year. When analyzed this model results, it is concluded that these diameter increment values are decreasing while stand age and stand density degree is increasing. With using this model, it is possible that diameter increment of single tree for various stand age and stand density degree of Brutian pine located in Aglasun Forest Enterprise are predicted for similar stand characteristics. The diameter increment prediction obtained by this model can be utilized for forest sciences and other purposes. Keywords: Stand age, Plantation, Stand density degree, Basal area