General equations are derived for the following optimised parameters in column chromatography: (a) The minimum analysis time for a specified separation number (Equation 14) in gas and liquid chromatography (GC and LC) when the pressure drop is limiting (Equation 25). (b) The minimum analysis time in GC and LC for a specified separation number when the particle diameter is fixed but pressure unlimited (Equations 30 and 33). (c) The maximum separation number which can be achieved in GC and LC with a given pressure drop and particle size irrespective of time (Equation 36). (d) The minimum pressure requirement for a given separation number and particle size in GC and LC (Equations 37 and 38). (e) The range of values of parameters for analysis with a specified separation number in a stated time. The equations are applied to practical cases. They indicate that severe technological problems will arise in the quest for optimum performance in LC, particularly in the design of microinjection and detection equipment. Progress in the immediate future is most likely to be made by the design of column packing materials which give rise to flat h versus ı curves (see Equations 18 and 19).