 To address these needs, we will conduct a preliminary, randomized, double-blind, placebo-controlled, 2 x 2 factorial chemoprevention trial n 88 of calcium 2,000 mgday and vitamin D3 800 IUday, alone and in combination vs placebo over 6 months in patients with recent removal of sporadic adenomatous colorectal polyps, to investigate their effects on the individual components and aggregate profile of our colorectal cancer risk biomarker panel. We will also examine study results stratified by NSAID use and Bsm I vitamin D receptor genotypes. The preliminary estimates of treatment effect sizes and variabilities will be used to refine the biomarker panel and study design and to calculate the needed sample size for a potential full-scale study. 