SIR97 is the integration of two programs,SIR92 andCAOS, the first devoted to the solution of crystal structures by direct methods, the second to refinementvialeast-squares–Fourier procedures. Several new features have been introduced inSIR97 with respect to the previous version,SIR92: greater automatization, increased efficiency of the direct methods section, and a powerful graphics interface. The program also provides publication tables and CIF files.