Prostate cells respond to estrogens, insulin, and other factors largely regulated in men by adipose mass. Several recent studies report obesity associated with high-grade prostate cancer, progression, and mortality, however the association with low-grade cancer common in the PSA era remains unclear. Challenges include measuring fat deposition patterns, excluding latent cancer from control groups, and controlling for several potential biases associated the effects of obesity on prostate cancer detection. Our study aims to address these challenges and determine the relationship between total adiposity (e.g., BMI, estrogens) and visceral adiposity (e.g., waist circumference, WHR, insulin) across high-grade cancer, low-grade cancer, and prostatic intraepithelial neoplasia (PIN). Preliminary analyses (R21 CA98348, n=304 cancer, 120 PIN, 424 controls) found WHR significantly associated with PIN (WHR>1.03: OR = 4.75 95% Cl (1.71, 13.2), ptrend<0.01, adjusted for PSA, BMI, prostate volume, age race, ORE result, # cores). Also, BMI>35 was associated with high-grade (Gleasons7) cancer (ORadj=3.49 (0.84, 14.4), ptrend = 0.05). Thus, visceral adiposity and the related metabolic syndrome may impact early prostate carcinogenesis, while an estrogen- rich environment associated with greater BMI may accelerate progression to high-grade/clinically relevant disease. Using our established multi-centered rapid-recruitment protocol, we will recruit an additional 1,106 prostate cancer cases (42% Gleason &7), 435 PIN cases, and 1,544 controls without cancer or PIN at prostate biopsy. Data and specimens (questionnaires for diet, physical activity, and other risk factors;body measures for BMI, WHR, sitting height, and % body fat (BIA);blood for DNA and hormone levels) are collected before diagnosis. Genes representing pathways linking total adiposity (e.g., Lep, LepR, CYP19, ER,AR, SHBG) or visceral adiposity (Res, Adip, AdipR1/2, INS, IRS1/2, IGF1, IGFBP3, PPARy2) to PIN or cancer will be investigated using multivariable logistic regression. Also, we will investigate blood markers of adiposity and PIN in an individually matched analysis (total adiposity: leptin, E2/T ratio, SHBG;visceral adiposity: HbA1c, adiponectin, resistin). Obesity is epidemic in the U.S., and prostate cancer is a leading cause of cancer-related death. Ongoing chemoprevention studies target PIN, and our results may identify new obesity-based prevention approaches or improve the prognosis of prostate cancer patients.