A series of 2-hydroxy-3-alkyl-1,4-naphthoquinones has been synthesized; the compounds have been screened as potential coccidiostats. Six of the new quinones have activity against Eimeria brunetti infections in chickens with 0.0125% of compound in the feed. The alkyl groups imparting greatest activity are 3-(4-cyclopentylphenyl)propyl, 3-(4-cycloheptylphenyl)propyl, 3-[4-(3-pentyloxy)phenyl]propyl, and 3-[4-(4-heptyloxy)phenyl]-propyl. In a series of quinones having 3-(4-alkoxyphenyl)propyl side chains, the activity increases with increasing lipophilicity of the alkoxy group. This parallels the effect first observed by Fieser, et al., for the antimalarial activity of 2-hydroxy-3-alkyl-1,4-naphthoquinones. © 1968, American Chemical Society. All rights reserved.