Daily average oleoresin exudation pressure (OEP) of 40-year-old loblolly pines was not significantly reduced until severe soil and atmospheric moisture stress occurred from mid-September to mid-October. Under these conditions OEP was reduced more in trees on flat, usually wet sites than in trees on low (0.3-0.6 m) mounds. This response is attributed to a deficient fine root system on flat sites.