The continuing philosophical interest in the famous 'Protocol Sentence Debate' in the Vienna Circle of Logical Positivists is, to a large measure, due to the focus on the epistemological issues in the dispute, and the neglect of differences among the leading players in their philosophical views of logic and language. In Protocols, Truth and Convention, the current understanding of the debate is advanced by developing the contemporaneous views of logic and language held by the principal disputants. Rudolf Carnap and Moritz Schlick. It is argued - largely on the basis of unpublished manuscripts and correspondence - that, despite apparent differences in their respective conceptions of language, there are nonetheless striking similarities, particularly with respect to the conventionality of language. Nonetheless, one key issue - concerning the syntacticism inherent in Carnap's early Thirties' philosophy - separates the two viewpoints in the clash over protocols. Finally, it is argued that Carnap's syntacticism is untenable, a conclusion that Carnap himself finally reached in the closing exchanges of the protocol sentence controversy.