Radiographic findings of 113 submucosally invasive colorectal cancers (CRCs) <or=20 mm were investigated by two observers to examine whether barium radiography is predictive of the invasion depth in small colorectal cancer. Smooth surface, central barium fleck, fold convergency and eccentric rigidity were chosen as the radiographic determinants. Predictive values of the determinants for deep submucosal invasion were compared between 45 CRCs <or=10 mm and 68 CRCs >10 mm. 47 CRCs had invaded the submucosa superficially while 66 CRCs had invaded deeply. The concordance rate in the assessment of radiology was 90.3% in smooth surface, 92.9% in central barium fleck, 90.3% in fold convergency and 79.6% in eccentric rigidity. Positive predictive value of central barium fleck for deep submucosal invasion was significantly higher in CRCs>10 mm than in those <or=10 mm (0.86 vs. 0.64, p=0.034). In contrast, negative predictive values of smooth surface (0.89 vs. 0.34, p<0.00001), central barium fleck (0.87 vs. 0.38, p=0.0002), fold convergency (0.64 vs. 0.33, p=0.0023) and eccentric rigidity (0.79 vs. 0.48, p=0.023) were significantly higher in CRCs <or=10 mm than in those >10 mm. These findings suggest that barium radiography is a procedure which can give useful information in prediction of invasion depth in CRCs <or=10 mm in size.