As in any complex architecture, debug and instrumentation resources are critical for multicore design. Debug instrumentation provides information for post-silicon debug analysis, software optimization, and performance monitoring. In this chapter, we introduce debug concepts useful for multicore; we deconstruct and discuss different debug instrumentation blocks and interfaces, including typical operations and system integration; and we discuss differences, considerations, and approaches more appropriate to multicore debug. This is followed by multicore debug examples, some of which are based on open standards and some on commercially-available blocks from processor IP providers.