Recent epidemiologic studies have shown a strong association between the relatively high doses of pediatric CT and the risk of cancer. Quantifying organ doses, as a measure of the risk, is commonly based on either direct anthropomorphic phantom measurements or Monte Carlo simulation. The major disadvantage in the phantom approach is its high cost especially that, for pediatric CT dosimetry, various phantom sizes are required to represent different age groups of children. On the other hand, Monte Carlo simulation, although not considered costly, requires validation by anthropomorphic phantom measurements. The aim of this project was to develop two methods of organ dose estimation in pediatric CT: 1) from the measured surface dose using optically stimulated luminescence dosimeters (OSLDs) and 2) by measuring the circumference of the body part being scanned as well as knowing the scan parameters. The project was based on a study proposed by the surgery department to monitor radiation exposure to children during their CT examination in the ER. A total of 200 pediatric patients were enrolled in this study which used OSLDs to monitor the doses. Specific aim 1 of this project was to characterize the OSLDs in the diagnostic energy range. Specific aim 2(a) was to find relationships between the patients' doses from OSLDs and both scan CTDI and the measured circumference. In specific aim 2(b) we carried out measurements using CTDI phantoms to investigate the relationships studied in specific aim 2(a). Specific aim 3 was to come up with models to estimate select organ doses from measuring surface dose or by using the circumference of the body part. To do this, pediatric examinations were simulated using a set of pediatric anthropomorphic phantoms in which doses of select organs were measured.