Compositions, such as pharmaceutical compositions, comprising specific diarylhydantoin and diarylthiohydantoin compounds, or salts or solvates thereof, are provided. Isolated and purified forms of the compounds are also described, as are unit dosage forms, compositions of substantially pure compound and kits comprising the compounds. The compounds and pharmaceutical compositions thereof may find use in the prevention and/or treatment of a variety of conditions, including prostate cancer, Parkinson's disease, Alzheimer's disease, and others.