The genetic determinants of in vitro resistance to the two drug components of SP individually are shown to be point mutations at seven sites in the dihydrofolate reductase gene (dhfr) causing resistance to pyrimethamine and five sites in the dihydropteroate synthase (dhps) gene causing resistance to sulphadoxine. Different combinations of mutations within each gene confer differing degrees of insensitivity. Due to administrative instability, until recently few molecular data relating to P. falciparum SP resistance markers have been available from within the borders of Afghanistan. However the investigators have obtained recent (submitted) data showing that in addition to two resistance polymorphisms in DHFR (C59R and S108N) that are well known to be at high frequency in the region, a small number of parasites in the Kunar province have three mutations (A437G, K540E and A581G) in DHPS.