The chapter explores reflections on the practice of letter-writing, with equal attention to instructional handbooks (esp. Demetrius’ Περὶ ἑρμηνείας‎, Iulius Victor’s Rhetorica, Pseudo-Demetrius’ Τύποι ἐπιστολικοί‎, Pseudo-Libanius’ Ἐπιστολιμαῖοι χαρακτῆρες‎, and Erasmus of Rotterdam’s De conscribendis epistolis) and the meta-generic statements that letter-writers routinely embed in their correspondence (with a special focus on Cicero, Ovid, Seneca, and Pliny the Younger). In both types of sources, what one might call the social dimension of style registers as a primary concern: in order for the letter to fulfil its purpose, namely to generate a special bond between sender and recipient, the chosen idiolect has to be ‘appropriate’ (πρέπον‎/aptum) to the interpersonal relationship and its specific circumstances and exigencies. Shared stylistic values and the willingness of the letter-writer to adjust his character to that of the recipient generate a sense of community between the correspondents.