The present invention is directed to crystalline forms of 6-[[(3S,4R)-3,4-dihydro-3-hydroxy-6-[(3-hydroxypheny)sulfonyl]-2,2,3-trim- ethyl-2H-1-benzopyran-4-yl]oxy]-2-methyl-3(2H)-pyridazinone, formulations containing at least one of these crystalline forms and their use to promote hair growth.