Crystalline forms of the anti-HCV compound (1aR,5S,8S,9S,10R,22aR)-5-tert-butyl-N-[(1R,2R)-2-(difluoromethyl)-1-{[(1-methylcyclopropyl)sulfonyl]carbamoyl}cyclopropyl]-9-ethyl-18,18-difluoro-14-methoxy-3,6-dioxo-1,1a,3,4,5,6,9,10,18,19,20,21,22,22a-tetradecahydro-8H-7,10-methanocyclopropa[18,19][1,10,3,6]dioxadiazacyclononadecino[11,12-b]quinoxaline-8-carboxamide (Compound I) were prepared and characterized in the solid state: Also provided are processes of manufacture and methods of using the crystalline forms.本發明關於製備抗HCV化合物(1aR,5S,8S,9S,10R,22aR)-5-三級丁基-N-[(1R,2R)-2-(二氟甲基)-1-{[(1-甲基環丙基)磺醯基]胺甲醯基}環丙基]-9-乙基-18,18-二氟-14-甲氧基-3,6-二側氧基-1,1a,3,4,5,6,9,10,18,19,20,21,22,22a-十四氫-8H-7,10-伸甲基環丙烷[18,19][1,10,3,6]二氧雜二氮雜環十九烷並[11,12-b]喹噁啉-8-羧醯胺(化合物I)之晶形和彼於固態之特性:本發明亦提供製備該晶形之方法和使用該晶形之方法。