Derivatives of the sesquiterpene 8-deoxyhemigossylic acid (2,3-dihydroxy-6-methyl-4-(1-methylethyl)-1-naphthoic acid) were synthesized that contained altered alkyl groups in the 4-position and contained alkyl or aralkyl groups in the 7-position. These substituted dihydroxynaphthoic acids are selective inhibitors of human lactate dehydrogenase-H (LDH-H) and LDH-M and of lactate dehydrogenase from the malarial parasite Plasmodium falciparum (pLDH). All inhibitors are competitive with the binding of NADH. Selectivity for LDH-H, LDH-M, or pLDH is strongly dependent upon the groups that are in the 4- and 7-positions of the dihydroxynaphthoic acid backbone. Dissociation constants as low as 50 nM were observed, with selectivity as high as 400-fold.