The purpose of this study is to introduce the application of new approaches to the determination of human colonic epithelial cell kinetic parameters. The isolation of pure and intact colonic epithelium from both surgical and biopsy specimens forms the basis of these approaches. The isolated epithelium is used in the determination of cell kinetic parameters by (a) flow cytometry, (b) Coulter counting, (c) dried cell preparations, and (d) crypt squashes. Using these methods, the following results were derived. The proportion of cells in the various phases of the cell cycle in the sigmoid epithelium was determined to be 81.6% +/- 2.15% (means +/- SE) in G1/G0 phase, 15.2% +/- 1.86% in S phase, and 3.2% +/- 0.62% in G2 + M phases. In the rectal epithelium, there were 79.6% +/- 3.35% in G1/G0 phase, 16.4% +/- 4.86% in S phase, and 4.08% +/- 1.90% in G2 + M phases. The total cell population in sigmoid epithelium was approximately 4.2 X 10(6) +/- 5.46 X 10(5) cells per cm2, and there were approximately 2.5 X 10(3) +/- 1.57 X 10(2) cells in each colonic crypt. Therefore, the number of crypts per square centimeter of human sigmoid mucosa could be estimated to be approximately 1.68 X 10(3). Lastly, in sigmoid epithelium, columnar cells of human sigmoid mucosa could be estimated to be approximately 1.68 X 10(3). Lastly, in sigmoid epithelium, columnar cells accounted for 76.3% +/- 6.18% of the epithelial cells, whereas the remaining epithelial cells, 23.7% +/- 4.08%, consisted of mucous cells.