Background: Fudosteine, (-)-(R)-2-amino-3-(3-hydroxypropylthio)propionic acid, is a cysteine derivative that was approved in Japan, as a new mucoactive agent. The aim of this study was to evaluate the tolerability and pharmacokinetics (PK) of fudosteine in healthy Korean subjects. Methods: A randomized, open-label, parallel, escalating single-dose study was conducted in 16 healthy Korean male subjects. The subjects were allocated to single-dose groups of 400 or 800 mg. Serial blood samples for PK analysis were collected immediately prior and after dosing up to 24 hours, and plasma concentrations were determined by high performance liquid chromatography (HPLC). Safety profiles were evaluated by monitoring adverse events and clinical evaluations throughout the study. Results: Median time to peak concentration ($T_{max}$) of both dosing group were around 0.5 hours and half-life ($t_{1/2}$) were around 3 hours. Mean peak concentration ($C_{max}$) of 400 mg and 800 mg dosing group were 10.8 and 21.5 ${mu}g/mL$ and the mean area under the plasma concentration versus time curve from the dosing time to infinity ($AUC_{inf}$) were 26.8 and 55.0 ${mu}g{cdot}h/mL$, respectively. Mean dose-normalized $C_{max}$ were 0.0271 and 0.0269 ${mu}g/mL/mg$ (P=0.923), respectively and dose-normalized $AUC_{inf}$ were 0.0669 and 0.0688 ${mu}g{cdot}hr/mL/mg$ (P=0.093), respectively. Fudosteine was well tolerated without any serious adverse events or clinical laboratory abnormalities. Conclusion: This study showed that fudosteine has a linear PK property and is well tolerated within 800 mg in healthy Korean volunteers.