Abstract: AIM: The pharmacokinetic profile of a new injection formulation of 124 mg norfloxacin (I) after intramuscular injection was studied and compared with that of a 124 mg marketed oral I capsule. METHODS: The norfloxacin intramuscular injection and the oral norfloxacin capsule were given to 8 healthy male subjects (aged 20～30 years) in a randomized crossover study. The determination of the I serum concentration was carried out by high performance liquid chromatography. RESULTS: The pharmacokinatic profiles of the norfloxacin intramuscular injection and the oral norfloxacin capsule may be fitted to a two- and one-compartment open model, respectively. The pharmacokinetic parameters were estimated by using the nonlinear least square computer program on basis of the compartment model. The noncompartmental pharmacokinetic parameters were also calculated on basis of the statistic moment theory. The injection (im) gave an area under the curve (AUC) 1.34-fold higher, a peak concentration (C_max) 1.5-fold bigger and a time to C_max (T_max) 3.5-fold shorter than those of the capsule (po) (P<0.05). The systemic clearance (Cls) and mean residence time (MRT) for injection (im) was 21.80 L.h^-1 and 7.32 h respectively, compared with 31.15 L.h^-1 and 6.16 h for the capsule (po) (P<0.1). CONCLUSION: The intramuscular norfloxacin injection (im) was better and more rapidly absorbed and more slowly eliminated than the oral capsule (po).