Background : Phase I tolerance and pharmacokinetic studies of Q-35, a newly synthesized fluoroquinolone antibiotic. were performed in healthy male volunteers. Drug safety and pharmacokinetic profiles were evaluated after single oral administration. The effect of food on pharmacokinetics of Q-35 was also evaluated. Methods : Twenty seven young healthy male were randomly assigned to the dose,.escalation schedule after screening by physical and laboratoy examinations. After pilot evaluation of safety by 50mg single oral administration in three volunteers. the dosage was increased to 100, 200, 400mg for each group which was composed of 2 placebo and 6 Q-35 administered subjects. In addition to the pharmacokinetic evaluation. physical and laboratory examinaions including CBC, blood chemistry, urinalysis,. body sway test ECG, and slit lamp examination were performed to evaluate the safety of Q-35. Food interaction study was performed in 200mg administered group by crossover method. Results : No volunteers complained of any subjective symptoms related with Q-35 administration. Physical and labortory examinations did not show any significant changes after the drug administration except for some fluctuations in heart rate and blood pressure which were supposed to be due to the circardian variations in comparison with those of placebo administered volunteers. Q-35 was rapidly absorbed and its peak plasma concentration increased linearly in dose dependent fashion. Cmax and AUCs ranged $0.57-4.31{mu}g/ml$ and $2.6-31.6{mu}g/ml*hr$ in proportion to the administered dose. but half-lives of Q-35 were consistent in the range of 6.5-7 hours regardless of dose. Cumulative Q-35 excretion in 48 hour collected urine was as much as 45-68% of administered dose. Q-35 penetrated distributed to saliva after oral administration. The AUC ratio of saliva to plasma was 0.55. Time to peak drug concentration changed from $1.3{pm}0.5$ hours of fasting state to $1.8{pm}1.1$ </TEX> hours after food intake. Tmax changed from $1.3{pm}0.5$ hours of fasting state to $1.8{pm}1.1$1 hours after food intake. Tmax changed from $1.3{pm}0.5$ hours of fasting state to $1.8{pm}1.1$ hours after food intake. Cmax changed form $2.0{pm}0.6$ to $1.5{pm}0.4{mu}g/ml$. Food interaction resulted relative bioavailavility to be 84.3% compared to that of fasting state. In all dose groups Q-35 was rapidly distributed to saliva to the extent of 54-75% of AUC ratio(saliva/plasma) and half-lives of saliva concentration were similar to those of plasma. Conclusion : We concluded that Q-35 is tolerable in maximum 400mg single dose with desirable pharmacokinetic profile as a systemically administered antibiotic. The result of this study would be applicable for repetitive administration study and phase II study.