Loblolly pine (Pinus taeda L.) seedlings of five half-sib families were grown for 3 yr in the field in open-top chambers. The seedlings were fumigated during the growing seasons (approximately April-October) with ozone at the following target levels: subambient (CF), ambient (AMB), and ambient+ 60 ppb (AMB +). At the end of the three growing seasons, no significant ozone effects on diameter, height or total biomass of the seedlings were detected, and no statistically significant ozone-family interactions were detected. Analysis of growth trends suggest that drought during the second and third growing seasons may have interacted with the ozone treatments. The importance of long-term studies under realistic field conditions is discussed.