Fluoroquinolones are used worldwide in the treatment of severe infections. These drugs, however, can interact with other agents. This paper is a review of drug interactions with different quinolone derivatives at the absorption phase; the review deals mainly with the prototype quinolones, ciprofloxacin and ofloxacin, and also with some of the newer agents. The concomitant agents considered are food, H2-receptor antagonists, anticholinergic drugs and metallic cation-containing compounds. Food (standard breakfast), H2-receptor antagonists and anticholinergic drugs had no major effect on the bioavailability of the quinolones. However, antacids, ferrous sulfate and other metallic cation-containing compounds impaired the bioavailability of the quinolones. This effect is due to chelation between the functional groups of the quinolone molecule and the metallic cations, resulting in insoluble complexes that can be absorbed. The degree of impairment varied between different quinolone derivatives.