Background: LB80380 is a prodrug of LB80317 developed for the treatment of wild type and lamivudine resistant hepatitis B. This study was conducted to evaluate the pharmacokinetics of LB80380 and that of LB80920 and LB80331 which are the metabolites of LB80380 in healthy volunteers. Methods: This was an open-label, 1-sequence, 2-treatment crossover study. LB80380 90 mg was administered in period 1 and LB80380 240 mg was given in period 2. Blood samples for pharmacokinetics were collected up to 24 hours after each dosing. LB80380, LB80920 and LB80331 were analyzed by liquid chromatography-tandem mass spectrometry. Safety was assessed by monitoring for adverse events (AEs), vital signs, ECGs, physical examination, and laboratory tests. Results: LB80380 was not detected during all sampling times in all subjects. LB80920 was detected up to 3 hours with a median peak time of 0.5 hr for 90 mg and 0.75 hr for 240 mg. LB80331 reached peak plasma concentration at 2.0 hr for both 90 mg and 240 mg. $C_{max}$ of LB80331 were $215.4{pm}29.4;{mu}g/L$ (mean ${pm}$ SD) and $421.4{pm}140.1;{mu}g/L$; AUCinf was $1280.2{pm}285.3;{mu}g{ast}h/L$ for 90 mg and $2555.4{pm}508.3{mu}g{ast}h/L$ for 240 mg. A total of 3 adverse events were reported and judged as mild intensity. Conclusion: Pharmacokinetic profiles after administration of LB80380 were in accordance with invitro data in which LB80380 was rapidly metabolized to LB80920 and then to LB80331. A single administration of LB80380 was generally safe and well tolerated.