The establishment and characterisation (morphology, ultrastructure, tumourigenicity) of six cell lines from primary human colorectal adenocarcinomas is described. These lines were established from surgical specimens, from 49 unselected patients, without the use of 'feeder' cells, 'conditioned' medium or passage of cells in nude mice. The six cell lines exhibit considerable variation in morphology, CEA secretion and tumourigenicity in nude mice. At least two of the lines retain some of the differentiated characteristics of colorectal epithelium.