Among the different methods used to increase the aqueous drug solubility, the preparation of a solid dispersion with a soluble carrier represents an interesting formulative approach. We substituted polyvinylalcohol with triethyleneglycolmonoethylether and obtained a suitable material for the formulation of a solid dispersion of progesterone, by spray-drying. In particular, we evaluated the influence of the polyvinylalcohol substitution degree and the polymer-drug weight ratios in the preparative mixture on the progesterone dissolution rate in the aqueous environment.