New advances in AFIS optical technology and measurement algorithms have enabled the measurement of cotton fineness and maturity parameters and their associated distributions. General classifications of fineness, immature fiber content, and maturity ratio values have been established drawing on traditional research results and on new in-mill application studies. Application results for raw material, opening and cleaning lines, carding processes, and fabric analyses are presented which show the importance of knowing and being able to control not only the average maturity and fineness of a laydown of cotton but also the distribution of fineness and maturity throughout the spinning process.