Nondeterministic pauses in traditional garbage collection (GC) have inhibited Java technology from being a suitable environment for real-time (RT) development. Metronome GC -- part of IBM WebSphere Real Time -- provides deterministic GC behavior that, when combined with other features, enables developers to write hard RT applications in the Java language. The authors describe the approach that Metronome uses for deterministic GC, technical issues involved in developing Metronome, and the tools and facilities available for tuning GC.