The study will assess the impact that insecticide resistance has on the effectiveness of malaria vector control tools LLIN and IRS. This is done by a cluster randomised trials of universal coverage LLINs versus universal coverage LLINs in combination with IRS, with levels of baseline insecticide resistance in the main vector balanced between the two study arms. In each cluster resistance to the insecticide used on LLINs is monitored, and malaria incidence is estimated from cluster specific cohorts of children followed up over the duration of the study. Resistance impact will be assessed from the ratio of incidence rates in clusters with high compared to those with low resistance and from a continuous measure of resistance expressed as percentage loss of mosquito mortality when exposed to insecticide in standardised WHO tests. Resistance mechanisms will be studied in subsets of study clusters.