SnB is a computer program based on Shake-and-Bake, a dual-space direct-methods procedure for determining crystal structures from X-ray diffraction data. This program has been used in a routine fashion to solve difficult structures, containing as many as 1000 unique non-H atoms, that could not be solved by traditional reciprocal-space routines based on the tangent formula alone. Recently, SnB has also been used to determine the anomalously scattering substructures of selenomethionyl-substituted proteins containing as many as 160 Se sites. Generally, non-substructure applications require that diffraction data be measured to 1.1Å resolution or higher although some structures having several moderately heavy atoms (e.g. S or Cl) have been solved at 1.4Å. SAS or SIR substructure applications routinely use 3Å data and have been successful at a resolution as low as 5Å.