The General Large-Area Model for annual crops (GLAM) is a tool for assessing the impacts of climate variability and change on annual crops. It has been designed for use with regional and global climate model output and remotely sensed data. GLAM has a growing user community and the model is under continuing development. Below, the underlying concepts behind GLAM are explained, some results are presented, and some key references are provided. The model is available for non-profit use under a free license agreement.