Solvates and polymorphs of ritonavir and methods of making and using the same

Novel solvates and crystal polymorphs of Ritonavir are disclosed, as well as methods of making them. Specific solvates of the compound include a formamide solvate and a partially desolvated solvate. Also disclosed are methods of making previously known forms of Ritonavir. Methods of using the novel forms of Ritonavir for the treatment of diseases, such as HIV-infection, are disclosed, as are pharmaceutical compositions and unit dosage forms comprising the novel forms of Ritonavir.