Publisher Summary This chapter discusses the parallelism between production and comprehension in agrammatism. Until 1916, the term agrammatism was used to refer to any disorder in the production of sentence. Since then, agrammatism has been referred to the simplification of sentence form, chiefly reflected in the omission of function words and inflectional endings, and paragrammatism to a failure to produce a correct sentence form, manifesting itself in the incorrect use of sentence form elements. On the basis of different studies, it is now taken for granted that in agrammatism, the productive deficits are always accompanied by parallel deficits in comprehension. The three most recent approaches to agrammatism have all assumed that some processing component shared by production and comprehension processes is disrupted.