Spironolactone deposited from acetone and methanol onto glass particles in the forms obtained on recrystallisation, but adopted different forms on lactose due to the effects of solvent on the matrix.Solvent-deposition, the precipitation of solute onto a matrix surface by evaporation, is an established process in the manufacture of solid dosage forms, and is commonly used as a mixing technique. As reports of comprehensive studies on the effects of deposition systems on drug particle size, dissolution rate and stability had noted the occurrence of polymorphic behaviour1,2, it was considered of interest to examine whether forms with particular characteristics could be developed on solvent-dsposition. Spironolactone, a steroidal diuretic with variable and dissolution-dependent bioavailability3, was selected for study as it had been found to crystallise from volatile solvents in different forms exhibiting substantially different dissolution rates;4 powdered glass was employed as a model matrix.5This paper was presented in part at the 4th pharmaceutical Technology Conference, Edinburgh, April 1984.