The shape of a crystalline organic solid has a major impact on its downstream processing and on its end-product quality, issues that are becoming increasingly important in the specialty and fine chemical, as well as the pharmaceutical and life science, industries. Though it is widely known that improved crystal shapes can be achieve by varying the conditions of crystallization (such as solvent type and impurity levels), there is far less understanding of how to effect such a change. Until recently, most methods for predicting crystal shapes were based exclusively on the internal crystal structure, and hence could not account for solvent or impurity effects. New approaches, however, offer the possibility of accurately predicting the effects of solvents. Models for predicting crystal shape are reviewed, as well as their utility for process and product design.