The effect of stand factors on the limiting size-density relationship was studied. Management intensity, planting density, and site index significantly impacted the parameters of the limiting size-density relationship. Different fitting methods and mathematical forms were proposed to model the size-density trajectories. The mixed-effects analysis technique proved to be a valuable statistical approach for fitting the limiting size-density line and providing the opportunity to test the significance and impact of additional factors. A semiparametric interaction mixed model was able to completely describe the density-size trajectory of even-aged loblolly pine stands in the southeastern U.S.