The capabilities needed in an Ada debugger are discussed in light of the language's tasking constructs, and the design for a debugger is presented which operates in concert with a single-processor Ada interpreter. This debugger design demonstrates the extensions to sequential debugging techniques that are necessary to handle concurrency, and shows that significant debugging functionality can be provided even without the inclusion of automatic error diagnosis methods. The issues considered include isolation of effects and display of the full dynamic execution status, both of which are essential to diagnosis of concurrent programs.>