Long-lasting insecticidal nets (LLINs) in which wash-resistant formulation of insecticide is coated or incorporated into the netting of synthetic polymer fibres during manufacture are the most widely used method for malaria prevention in Africa and Asia. By 2021, 38% of the population at risk of malaria in Africa were sleeping under an ITN, compared to <2% in 2002. This coverage has made a major contribution to the halving of the global malaria burden over the last two decades. With the LLINs’ success, come new technical and logistical challenges that compromised their effectiveness. Major challenges facing LLIN intervention include inadequate LLIN coverage, inappropriateness in humanitarian emergencies and the evolution and spread of insecticide resistance. The work in this thesis was designed to identify and contribute to the solution of these problems. This required testing and evaluation in laboratory, experimental hut and field trials of several new LLIN products for purposes of product validation for WHO. It required improvement of WHO testing and evaluation guidelines to which we contributed, investigation of new long-lasting treatment kits to treat other types of materials to solve problems in niche situations and to help reduce gaps in LLIN coverage. To combat the problem of resistance required evaluation of alternative insecticides and synergists to curb the limitations of standard LLINs for control of resistant vector. This necessitated studying the added efficacy of alternative / combination insecticides alongside standard pyrethroid-only nets to control resistant vector populations, and meta-analysis of evaluations before and after the evolution of resistance. Along this journey the studies in this thesis have helped advance LLIN product quality, contributed to WHO guideline revision, helped solve outstanding problems of malaria vector control, and have investigated the durability of different synthetic polymers and alternative novel insecticides; and by so doing have helped advance malaria prevention.