Technical writing theory and research about communication in large organizations mostly ignore from-the-top control of rhetoric. The usual emphasis on an individual writer negotiating with a known audience and generally free to decide on matters of style, organization, and so on can hide the ways that power relations often silently control internal rhetoric. Conclusions are based on two case studies: In the later Middle Ages, professional letters had to conform to a rhetorical format that necessarily foregrounded unequal power relations. In a contemporary nuclear power station, similar power relations purposely obscure writer and audience while procedures dictate format and content.