Methylene blue (MB) is the oldest synthetic antimalrial. It is not used anymore as antimalrial but should be reconsidered. For this purpose we have measured its impact on both chloroquine sensitive and resistant Plasmodium strains. We showed that around 5 nM of MB were able to inhibit 50 % of the parasite growth in vitro and that late rings and early trophozoites were the most sensitive stages; while early rings, late trophozoites and schizonls were less sensitive. Drug interaction study following fractional inhibitory concentrations (FIC) method showed antagonism with amodiaquine, atovaquone, doxycycline, pyrimethamine; additivily with artemether, chloroquine, mefloquine, primaquine and synergy with quinine. These results confirmed the interest of MB that could be integrated in a new low cost antimalarial combination therapy.