During the course of several years research with cotton cell cultures, fibers were occasionally observed to form in vitro. Further investigations have subsequently resulted in a system of in vitro fiber development that may be used to study regulation of in vivo fiber development. Cells elongate and produce secondary cell walls. The time course of development is similar to that of in vivo fibers although length and maturity are much less. Efforts are being made to improve both length and maturity. The possibilities for improvement of fiber quality through study of gene regulation using in vitro fiber development are discussed.