Background: To determine the impact of the introduction of ă artemisinin-based combination therapy (ACT) on parasite susceptibility, ă a molecular surveillance for antimalarial drug resistance was conducted ă on local isolates from the Hopital Principal de Dakar between November ă 2013 and January 2014 and between August 2014 and December 2014. ă Methods: The prevalence of genetic polymorphisms in antimalarial ă resistance genes (pfcrt, pfmdr1, pfdhfr and pfdhps) was evaluated in 103 ă isolates. ă Results: The chloroquine-resistant haplotypes CVIET and CVMET were ă identified in 31.4 and 3.9 % of the isolates, respectively. The ă frequency of the pfcrt K76T mutation was increased from 29.3 % in ă 2013-2014 to 43.2 % in 2014. The pfmdr1 N86Y and Y184F mutations were ă identified in 6.1 and 53.5 % of the isolates, respectively. The pfdhfr ă triple mutant (S108N, N51I and C59R) was detected in the majority of the ă isolates (82.3 %). The prevalence of quadruple mutants (pfdhfr S108N, ă N51I, C59R and pfdhps A437G) was 40.4 %. One isolate (1.1 %) harboured ă the pfdhps mutations A437G and K540E and the pfdhfr mutations S108N, ă N51I and C59R. ă Conclusions: Despite a decline in the prevalence of chloroquine ă resistance due to the official withdrawal of the drug and to the ă introduction of ACT, the spread of resistance to chloroquine has ă continued. Furthermore, susceptibility to amodiaquine may be decreased ă as a result of cross-resistance. The frequency of the pfmdr1 mutation ă N86Y declined while the Y184F mutation increased in prevalence, ă suggesting that selective pressure is acting on pfmdr1, leading to a ă high prevalence of mutations in these isolates and the lack of specific ă mutations. The 50.5 % prevalence of the pfmdr1 polymorphisms N86Y and ă Y184F suggests a decrease in lumefantrine susceptibility. Based on these ă results, intensive surveillance of ACT partner drugs must be conducted ă regularly in Senegal.