Oscail is a program for small-molecule crystallography which includes crystal morphology prediction and an interface to molecular modelling. The Oscail graphical user interface can drive SHELX and Superflip for structure solution and SHELXL for structure refinement. The lattice analysis includes hydrogen bonding, halogen bonding and van der Waals contact stacking. Other facilities include interactive bar charts of space-group frequencies in the Cambridge Structural Database, powder diffraction pattern calculation and reduced cell cluster analysis of structures. The graphics output includes thermal ellipsoid plots and rendered OpenGL and Raster3D photorealism in stills and movies. The molecular modelling includes quantum calculations (MOPAC, extended Huckel and density functional theory) and TINKER molecular mechanics.