Bedaquiline and delamanid, novel classes of anti-tuberculosis drugs, have been recently approved for the treatment of multidrug-resistant tuberculosis. Antimicrobial resistance invariably follows the introduction of new drugs, and appropriate drug-susceptibility testing assays are needed to detect resistance and tailor treatment regimens that contain new agents. Given that phenotypic drug-susceptibility testing is slow, technically demanding, and, in some cases, unreliable, future assays are likely to be based on rapid molecular techniques. To design such assays, research to unravel the genetic basis of resistance is urgently required (appendix). The question is how to ensure that this research occurs in a timely way, before the emergence and spread of resistance.