It has been previously established that the housing condition influences the appearance of the dendritic tree in young animals. The purpose of this investigation was to determine the extent of the influence that the housing condition exerts on morphometric studies involving old animals. Specifically, we found superficial pyramidal cells from the visual cortex of socially aged 20-month-old rats had more extensive oblique dendritic trees than neurons from isolated rats of the same age. The basal dendritic tree of neurons from socially reared rats was denser nearest layer IV while the basal dendritic tree of neurons from isolated rats appeared to shift away from layer IV. Our results indicate that the external environment is an independent variable and cortical dendritic morphology is a dependent variable in studies on old adult rats. Thus, the external environment should be considered in reporting results of aging studies on dendritic topology.