Accurate detection of premalignant lesions and early cancers in the colon is essential for curative endoscopic or surgical therapy, since the prognosis for the affected patients is closely related to the size and stage of the neoplastic lesion. Total colonoscopy is the accepted gold standard for screening and surveillance of colorectal cancer. This review summarizes recently published diagnostic developments and key findings in the areas of colonoscopy, colonic tumors, and inflammatory bowel diseases.