Nuclear and structural abnormalities on the histological specimens of colorectal dysplasias were quantified by using 10 parameters. From the measured values, the following histological findings were obtained: progression from mild to severe dysplasia was associated with an increase in nuclear size, and nuclear arrangement became more irregular. There was, however, no difference between the nuclear size and arrangement in severe dysplasia and those in carcinoma. The nuclei were spindle shaped in mild and moderate dysplasia. On the other hand, they were relatively round in severe dysplasia and carcinoma. Structural abnormalities tended to increase with the histological abnormalities. These results correspond well with the histological abnormalities by which the pathologists grade dysplasia and diagnose carcinoma subjectively. Therefore, these 10 parameters might be useful for quantifying histological characteristics of colorectal dysplasias.