Speech acts are said to be conventional (i) in that there are conventional grammatical ways to indicate a type of speech act; (ii) in that a number of conditions have to be satisfied in order to perform a speech act felicitously (iii) in that there are certain compulsive patterns of behavior that follow the performance of speech acts; (iv) in that they belong to the regular procedures of certain institutions. A historical overview of the growth of the idea of the conventionality of speech acts is added (with reference to Wittgenstein, Austin, Strawson, Searle, Cohen and Grice).