The effect of vines on diameter growth of Liquidambarstyraciflua L. (sweetgum) in a 40-year-old abandoned field was measured by vine removal experiments. Removal of vines from the trunk branches and ground had a significant positive effect on growth during each of the 4 years of the study but removal of vines from only the trunk and branches did not produce a significant increase in growth. The data suggest that vines influence forest production by competing with trees even after trces have grown tall enough to avoid direct physical suppression.