Drug-resistant tuberculosis is a global problem, but the necessity and quality of intervention should be assessed by country since the causes of drug resistance, and thus the appropriate intervention strategies, may vary considerably between countries. An analysis of the development and spread of drug-resistant tuberculosis is presented and the respective roles of import of the disease and of HIV are discussed. A definition of inadequate treatment and a systematic approach to the quantitative and qualitative aspects of the drug resistance problem is proposed. The 'treatment delivery process' (TDP) is introduced as a diagnostic tool to analyse the causes of secondary (or acquired) resistance in a specific area. Intervention strategies should be based on the evaluation of this TDP. Intervention strategies and general aspects of their implementation are discussed.