Recent studies have suggested the potential involvement of multidrug resistance (mdr) genes in resistance to quinoline-containing compounds in Plasmodium falciparum parasites. Three different antibodies were used to detect the malarial mdr 1 protein product by indirect immunofluorescence and/or immunoblot in fresh clinical isolates and clones of P. falciparum from different geographic origins. A 160-kDa protein was detected in all five parasite clones by immunoblot and around the food vacuole by IFA, regardless of the level of sensitivity to chloroquine and the modulation by desipramine of chloroquine accumulation. Our results suggest that chloroquine resistance is not correlated with the presence of the Pfmdr1 product.