Significant mean height and mean diameter responses to nitrogen and phosphorus fertilization were observed 5 years after treatment in 31 loblolly pine stands located in the southeastern United States. Stands were consistently most responsive to the addition of 112N-56P kg/ha. Gains averaged 12% for all sites, and 31% for statistically responsive sites. Responses for other N or P rates were lower, but still positive and significant. Depending on the treatment, between one-fourth to one-half of the experimental installations exhibited a statistically significant positive response to fertilization. Twenty-two of 31 installations had significantly different height growth-diameter growth relationships following fertilization, although treatment effects were not consistent. Fertilizer-induced changes in H-D equation parameters were statistically nonsignificant for 27 of the 31 studies. Changes in H-D curve parameters associated with 1 or 2 year acceleration in stand development were small compared to the errors associated with fitting H-D curves to 15 or more years of cumulative height and diameter. For. Sci. 33(3):644-653.