is valid. The method could be applied in other contexts to estimate preintervention condom use rates for programme evaluation in the absence of baseline data. We recommend the inclusion of questions on duration of behaviours in programme evaluation surveys. The findings of the analysis indicate a positive relationship between implementation of the Avahan programme and rates of increase in consistent condom use among female sex workers. Acknowledgments This research was funded by the Bill & Melinda Gates Foundation. The views expressed herein are those of the authors and do not necessarily reflect the official policy or position of the Bill & Melinda Gates Foundation. MA is a national researcher of the Fonds de la Recherche en Sant du Qubec, Canada (grant no. 8722). . Scale-up and coverage of Avahan: a large scale HIV-prevention programme among female sex workers and men who have sex with men in four Indian states . Sex Transm Infect 2010 ; 86 ( Suppl 1 ): i76 -- 82 . Supplement : Changes in risk behaviours and prevalence of sexually transmitted infections following HIV preventive interventions among female sex workers in five districts in Karnataka state, south India Supplement : Quality assurance and quality improvement using supportive supervision in a large-scale STI intervention with sex workers, men who have sex with men/transgenders and injecting-drug users in India