Based on the evidence reviews, it is recommended that the MDR-TB regimen be composed of at least five drugs that are likely to be effective, i.e. four core second-line drugs plus pyrazinamide. If a minimum of four core second-line TB medicines cannot be reached by using agents from Groups A to C alone, drugs from Group D2 (in adults; delamanid may also be used in patients aged 6–17 years) or, if not possible, from Group D3 are added. Pyrazinamide is added routinely unless there is confirmed resistance from reliable DST, or well-founded reasons to believe that the strain is resistant, or there is risk of significant toxicity. If pyrazinamide is compromised or cannot be used, the regimen may also be strengthened with an additional agent from Groups C or D (preferably D2, or if not possible, from D3). Other agents from Group D1 are included if they are considered to add benefit (e.g. high-dose isoniazid in patients without high-level isoniazid resistance). The total number of TB medicines to include in the regimen needs to balance expected benefit with risk of harms and non-adherence when the pill-burden is high. The recommendations for children are mostly identical to those of adults. However, in children with mild forms of disease, the harms associated with Group B medications (secondline injectable agents) outweigh potential benefits and therefore Group B medications may be excluded in this group of children. The GDG based this decision on the observation that treatment success in children with clinically diagnosed disease (which was associated with less severe clinical or radiological manifestations) was high and not significantly different in patients treated with and without a Group B medication (93.5% versus 98.1%; n=219; see online Annex 4). In October 2016, WHO published its revised policy on the use of delamanid in patients aged 6–17 years following the advice of a separate Guideline Development Group convened expressly to review evidence for its effectiveness and safety in children and adolescents(6). Delamanid is now conditionally recommended for use in these age-groups as an add-on agent to a longer MDR-TB regimen. Lack of data at this stage on the use of bedaquiline in children precludes a recommendation in patients aged under 18 years. WHO recommends that all TB patients – children or adult – diagnosed with strains shown to be resistant to rifampicin be placed on a MDR-TB treatment regimen. In such cases, isoniazid is added alongside the rest of the MDR-TB regimen until susceptibility results are confirmed. If isoniazid susceptibility cannot be tested, isoniazid may still be added to the regimen unless there are well-founded grounds to consider the drug ineffective.