Based on the study results we conclude that: (1) In general, drying increases the flexural properties of Southern Pine dimension lumber. (2) Improvements in Moduli of Rupture (MOR) and Moduli of Elasticity (MOE) with drying are significant for Select Structural lumber at virtually all levels of the cumulative frequency distribution. The magnitude of the increase for mean MOE and fifth percentile MOR for Select Structural lumber appears to exceed that assumed in ASTM standard D245-81 for lumber dried to an equilibrium Moisture Content (MC) of 15%. (3) The degree of improvement in strength as lumber dries decreases as lumber quality decreases and width increases. For lower grades and wider widths, the 25% increase in fifth percentile MOR assumed in D245-81 appears excessive. (4) The effect of MC on MOE is relatively independent of lumber size and quality. (5) Drying lumber to an average MC less than 15% cannot usually be justified on the basis of improvements in flexural strength and stiffness.