Several enantiomerically pure (2,6dimethyl-4-pyridinyl)quinolones, previously shown to be potent inhibitors of bacterial DNA gyrase, exhibit topoisomerase II inhibitory activity. Among these and other analogues, topoisomerase II inhibitory potency was found to be a sensitive function of the size and substitution of the bridge spanning the l- and II-positions of the quinoline ring. The 6-fluoro group was requited for activity.