The kinetics of a single i.v. dose of theophylline given either alone or with flumequine was studied in eight healthy volunteers. No statistically significant differences were observed in the pharmacokinetic parameters of theophylline (volume of distribution, elimination half-life, AUC, plasma clearance) following the two treatments. Pretreatment for 5 days with oral flumequine (400 mg, three times daily) had no significant effect on the disposition of a single i.v. dose of theophylline in healthy volunteers.