Until now, there has been very little unified analysis of metadiscourse across speech and writing. Drawing on a reflexive metadiscourse model, this article conducts a multidimensional analysis of metadiscourse across 10 spoken and written registers in a corpus of 626 texts. Two metadiscourse dimensions, participants' interaction and discourse presentation, are identified. The more interactive registers are more prominently marked by participants' interaction, and the more informational registers by discourse presentation. Along metadiscourse dimensions, the 10 registers are lumped into 6 clusters: 'discussion broadcasts and public conversations', 'scripted speeches and unscripted speeches', 'general prose and nondiscussion broadcasts', 'press and fiction', 'casual conversations', and 'academic prose'. Metadiscourse markers of both dimensions are frequently used in registers of the first two clusters which are highly interactive and informational, while they rarely occur in registers of the next two clusters which have low interactive or informational focuses. Metadiscourse markers of participants' interaction are pervasive in the highly interactive register (casual conversations), and those of discourse presentation in the highly informational register (academic prose).