B A C K G R O U N D :Scaling up treatment for multidrugr esistant tuberculosis is a global health priority. However, current treatment regimens are long and associated with side effects, and default rates are consequently high. This systematic review aimed to identify strategies for reducing treatment default. M E T H O D S :We conducted a systematic search up to May 2012 to identify studies describing interventions to support patients receiving treatment for multidrugr esistant tuberculosis (MDR-TB). The potential influence of study interventions were explored through subgroup analyses. R E S U LT S : A total of 75 studies provided outcomes for 18 294 patients across 31 countries. Default rates ranged from 0.5% to 56%, with a pooled proportion of 14.8% (95%CI 12.4-17.4). Strategies identified to be associated with lower default rates included the engagement of community health workers as directly observed treatment (DOT) providers, the provision of DOT throughout treatment, smaller cohort sizes and the provision of patient education. C O N C L U S I O N : Current interventions to support adherence and retention are poorly described and based on weak evidence. This review was able to identify a number of promising, inexpensive interventions feasible for implementation and scale-up in MDR-TB programmes. The high default rates reported from many programmes underscore the pressing need to further refine and evaluate simple intervention packages to support patients. K E Y W O R D S : default; retention; MDR-TB THE MULTIDRUG-RESISTANT tuberculosis (MDR-TB) pandemic is rising in prevalence and global importance. There were an estimated 650 000 cases of MDR-TB cases worldwide in 2010, with <5% of all TB patients tested for multidrug resistance. 1 Historically, proportions of MDR-TB among TB cases have been highest in Eastern European countries, although in absolute numbers China and India now contribute 50% of all new MDR-TB cases. 2 Furthermore, in sub-Saharan Africa, the human immunodefi ciency virus (HIV) epidemic and limited resources for comprehensive MDR-TB programmes have aided the spread of MDR-TB and the emergence of extensively drugresistant TB (XDR-TB). 3 MDR-TB, defi ned as Mycobacterium tuberculosis resistant to isoniazid and rifampicin, is more costly and complex to treat than fully susceptible disease, with treatment typically lasting at least 18 months. XDR-TB is defi ned as MDR-TB with additional resistance to a fl uoroquinolone and a second-line injectable agent. 2 Current approaches to treating MDR-TB rely on lengthy treatment durations (typically a minimum of 20 months) using drugs associated with substantial toxicities, often resulting in high default rates. Other reported factors infl uencing treatment default include high costs of treatment for patients in settings where patients must pay, 4 indirect costs such as loss of wages, 5 increased poverty and sex discrimination, 6 dissatisfaction with health care worker attitudes, 7 limited knowledge and negative beliefs and attitudes to treatment, 8 ch...