Blood content and tumor oxygen level are important biomarkers and prognostic indicators in patients with colorectal cancer (CRC). However, noninvasive measurements of both quantities in human colon are limited. In this study, we extracted the total hemoglobin concentration (THC) and oxygen saturation (StO2) of normal, premalignant, and malignant colonic tissues in 27 patients using a diffuse reflectance instrument and algorithms based on the diffusion equation. The mean±standard error of THC and StO2 from all normal sites (n=26) is 93.4±17.1 μM and 67.2±3.7%, respectively. THC increased to 136.9±23.8μM and 153.8±38.6μM and StO2 decreased to 51.3±7.0% and 26.4±6.1% for premalignant and malignant tissues, respectively. The disease-to-normal THC ratios are 3.2±1.1 and 4.4±1.9 and the disease-to-normal StO2 ratios are 0.7±0.1 and 0.5±0.1 for premalignant and malignant tissues, respectively. These results demonstrate the feasibility of a robust optical method to assess colon THC and StO 2 at all stages of carcinogenesis in vivo so that the angiogenesis and hypoxia of the disease and the therapeutic role can be studied in CRC patients.