Advances in neonatal technology have improved survival rates of children born at lower and lower birthweight and after fewer and fewer weeks of gestation. However, these children are at increased risk of experiencing developmental delays. As weeks of gestation and birthweight decrease, the risk of developmental impairment and severity increases. Yet to be determined is whether premature birth and low birthweight (LBW) effect development differentially, and if the combined, have an additive effect on developmental outcomes. The first part of this study aimed to examine the independent effects of preterm birth and LBW in children at risk for developmental delays. Using the Battelle Developmental Inventory, Second Edition (BDI-2), differences in overall developmental quotient (DQ) scores and domain scores (i.e., adaptive, personal-social, communication, motor, cognitive) were assessed. In Part 1, were noted different developmental profiles for children born premature and/or LBW. Additionally, premature birth and low birthweight (PLBW) children exhibited the greatest impairment in all areas of development evaluated compared to their premature, LBW, and full term peers. The second part of this study aimed to examine the predictive value of weeks of gestation, birthweight, age, gender, and race on developmental outcomes. For Part 2, weeks of gestation, birthweight, age, gender, and race predicted statistically significant impairments in all the areas of development assessed with to varying degrees. These findings support the institution of early intervention, before clinical manifestations appear, and the importance of highly individualized interventions. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]