Eighteen healthy volunteers aged 22 to 37 (average 30.44 +/- 4.11 years) seeking fertility evaluation at the Fertility and Sterility Centre of the Medical Clinic of the University of L'Aquila Medical School were studied for norfloxacin concentrations in serum, urine and seminal plasma 14-15 h after taking two 400 mg doses of the drug. The extraction of the biological fluids and the high pressure liquid chromatographic (HPLC) assay were performed following a method described previously (1), with seminal plasma samples processed in the same way as serum samples. The results in urine and serum substantially confirmed the figures already established for norfloxacin concentrations in such fluids. Seminal plasma levels (average 4.78 +/- 2.69 micrograms/ml) were about 5 times higher than the corresponding serum levels (average 0.89 +/- 0.59 microgram/ml). The authors believe that such concentrations, attaining a therapeutic range in the seminal plasma after only two 400 mg doses of norfloxacin, support its use as an effective chemotherapeutic agent in the management of male genital infections that frequently account for subfertility conditions in young patients.