This study represents the results of a randomized, single dose, two-treatment, two-period crossover study in 18 healthy male volunteers to assess the bioequivalence of two tablets of 400 mg lomefloxacin. The two formulations were: Lomax((R)) (Julphar, United Arab Emirates) as the test formulation and Maxaquin((R)) (Searle, S.A., UK) as the reference formulation. The study was conducted at the College of Pharmacy, King Saud University, Riyadh, Saudi Arabia, jointly with;King Khalid University Hospital, Riyadh, Saudi Arabia. After overnight fasting the two products were administered as a single dose on two treatment days separated by a 1 week washout period. Serial blood samples were collected thereafter, for a period of 48 h. Plasma harvested from blood was analysed fur lomefloxacin by a sensitive, reproducible and accurate HPLC method. Various pharmacokinetic parameters including AUC(0-t), AUC(0-proportional to), C-max, T-max, T-1/2, K-elm and C-max/AUC(0-infinity) were determined from plasma concentrations for both formulations and found to be in good agreement with reported values. Statistical modules applied to AUC(0-t), AUC(0-infinity) and C-max revealed no significant difference in the two tested products. Based on these statistical inferences it was concluded that Lomax((R)) is bioequivalent to Maxaquin((R)). Copyright (C) 1999 John Wiley & Sons, Ltd.