Crystalline solid forms of the anti-HCV compound (S)-isopropyl 2-((S)-(((2R,3R,4R,5R)-5-(2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)-4-fluoro-3-hydroxy-4-methyltetrahydrofuran-2- yl)methoxy)(phenoxy)phosphorylamino)propanoate (Compound I) are described Also provided are processes of making and methods of using the crystalline forms.
