This chapter discusses theories of spelling and writing both old and new. It considers some disorders of the more peripheral aspects of writing extensive discussion of disorders of spelling will be left to Patterson. The chapter deals with some general considerations of the nature of writing itself that must constrain all efforts at theorising in this area. Of all the areas of cognition to come under the psychologist's microscope, spelling and writing are probably the ones in which cognitive neuropsychology has been most influential. In other domains, such as reading, speaking, or remembering, experimental cognitive psychology provided ready-made functional theories or models that cognitive neuropsychologists could use to shape their initial investigations. They could then support, contest, or develop those models using data gathered from brain-injured patients. In fact, the situation facing the modern cognitive neuropsychologist working on spelling and writing is reminiscent of that which faced the "diagram-makers" of the late nineteenth century.