Cinoxacin is an antibacterial drug belonging to the quinolone class used in the treatment of urinary tract infections due to common gram-negative pathogens. Considering the high frequency of urinary tract infections in elderly people where aging represents a physiopathological condition frequently requiring an adjustment of the dosage regimen, the pharmacokinetic behaviour of cinoxacin (500 mg/12 h) in aged patients was investigated to find out if age-dependent differences may be established. The main differences detected were a shift to 4 h of the Tmax and a partly reduced clearance in comparison with data referred to younger people. On the other hand the findings showed that no accumulation occurred. High urinary concentrations of cinoxacin, exceeding the MICs for most urinary tract pathogens were found up to the 12th hour after administration.