Abstract: The present invention relates to a method of and an apparatus for treating of textile substrates with a supercritical fluid. The textile substrates are formed as spools of yarn or rolled webs, and the supercritical fluid flows over and/or through them substantially perpendicular to their spool or winding axis. At that, the treatment temperature assumes different values during the treatment period. It is provided that during the treatment period, the treatment temperature values are set by at least two functions of the treatment time, and that the supercritical fluid is conditioned differently at the time the following function takes effect.