The resurgence of tuberculosis and emergence of drug resistant disease has stimulated fresh research into mycobacteriophage. Studies are currently underway to develop phage-based tools for therapeutic and diagnostic use. Previous attempts at mycobacteriophage therapy in experimentally infected animals were not successful and alternative strategies of phage delivery that enable killing of intracellular bacteria are required. Replication of mycobacteriophage provides a simple means of detecting viable bacteria and good progress has been made towards the development of new phage-based diagnostic tools. When screening isolates for resistance to the major antituberculosis drug rifampicin phage-based tests have been shown to have high sensitivity. For the diagnosis of pulmonary tuberculosis evaluation studies indicate that current phage tests are not as sensitive as traditional culture methods. Further trials are needed to determine whether they might have a role in the detection of smear negative tuberculosis. A second generation of phage tests are under development following the construction of luciferase reporter phage. Preliminary data suggests they may offer rapid detection of mycobacteria and simple screening for drug resistance. The potential of mycobacteriophage to detect and treat other mycobacterial diseases remains largely unexplored.