The emergence of pyrethroid resistant Anopheles funestus (a major African vector) in malaria affected parts of KwaZuluNatal, South Africa was correlated with the malaria epidemic of 1996 2000. This finding prompted the necessity of incorporating insecticide resistance management strategies into formal malaria control policy in South Africa. Resistance management strategies often rely on the assumption of reduced fitness associated with insecticide resistance and are based on the principle that resistance genes will tend to drift out of vector populations in the absence of insecticide selection pressure. This study aimed to determine whether a fitness cost is associated with pyrethroid resistance as well as to determine the stability and mode of inheritance of the resistance genes in a pyrethroid resistant (FUMOZR) strain of An. funestus. It also aimed to sequence and analyze a segment of the sodium channel gene for any kdrtype mutation(s) that may be associated with pyrethroid resistance. The final aim was to determine the resistance mechanisms involved in a Ghanaian field population of An. funestus resistant to DDT and pyrethroids. Results obtained suggest that pyrethroid resistance in southern African An. funestus did not incur any loss of fitness. FUMOZR had a reproductive advantage over a pyrethroid susceptible An. funestus strain (FANG) in terms of higher fertility, proportion of females laying eggs and eggtoadult survivorship, and a lower sterility Click to buy NOW! PDFXCHANGE www.docutrack. com Click to buy NOW! PDFXCHANGE www.docutrack. com iv rate. However, FUMOZR had a slower developmental time from egg hatch to adult emergence than FANG. Results of crosses and backcrosses carried out between FUMOZR and FANG were consistent with a monofactorial and autosomal mode of inheritance in which the resistant genes presented as incompletely dominant. The resistant gene was found to be stable over several generations in the absence of insecticide selection pressure. Analysis of the genomic and mRNA sequences of the IIS5 IIS6 segment of the sodium channel gene showed a high sequence identity between FUMOZR and FANG suggesting that the two strains are genetically similar. The kdrtype mutation was absent from this region supporting previous evidence that the resistance mechanism is primarily metabolic. Bioassay data showed that a Ghanaian field population of An. funestus from Obuasi, Ghana, was resistant to DDT and pyrethroids. Molecular analysis of the IIS5 IIS6 segment of the sodium channel gene showed an absence of kdrtype mutations previously associated with insecticide resistance. Biochemical analysis suggests that resistance is metabolically mediated primarily by elevated levels of and esterases with monooxygenases and GSTs playing a lesser role. The presence of an altered acetylcholinesterase conferring carbamate resistance was also evident in the population. These results have implications for the management of resistance in malaria control programmes in Africa.