This multicenter study will be conducted by 18 colonoscopists from 5 hospitals in Taiwan, including Evergreen general hospital, E-da hospital, E-da Dachang hospital, Linkou Chang Gung memorial hospital, and Keelung Chang Gung memorial hospital, and plans to recruit 2700 prospective participants in a 2-year period. Felix W. Leung from Sepulveda Ambulatory Care Center, Veterans Affairs Greater Los Angeles Healthcare System (USA) will be involved in the study design, and will participate in data analyses and report preparation. Consecutive patients aged ≥50 years undergoing colonoscopy are eligible for enrollment. Positive fecal immunochemical test (FIT+) is considered as an independent indication category and the colonoscopy indications are categorized into 4 groups: screening, surveillance, diagnostic, and FIT+. Overall indication will be subdivided into overall excluding FIT (overall-non-FIT) group and overall including FIT (overall-FIT) group. In this study, the investigators plan to (1) compare individual ADR across 4 colonoscopy indication categories (screening, surveillance, diagnostic, FIT+); (2) explore correlations between screening ADR and overall-non-FIT and overall-FIT ADRs, respectively.