AIM To investigate the clinical implications of infliximab trough levels(IFX-TLs) and antibodies to infliximab(ATI) levels in Crohn’s disease(CD) patients in Asian countries. METHODS IFX-TL and ATI level were measured using prospectively collected samples obtained with informed consent from CD patients being treated at Asan Medical Center, South Korea. We analyzed the correlations between IFX-TLs/ATI levels and the clinical activity of CD(quiescent vs active disease) based on the CD activity index, C-reactive protein level, and physician’s judgment of patients’ clinical status at enrollment. The impact of concomitant immunomodulators was also investigated. RESULTS This study enrolled 138 patients with CD(84 with quiescent and 54 with active disease). In patients with quiescent and active diseases, the median IFX-TLs were 1.423 μg/mL and 0.163 μg/mL, respectively(P < 0.001) and the median ATI levels were 8.064 AU/m L and 11.209 AU/m L, respectively(P < 0.001). In the ATI-negative and-positive groups, the median IFXTLs were 1.415 μg/mL and 0.141 μg/mL, respectively(P < 0.001). In patients with and without concomitant immunomodulator use, there were no differences in IFX-TLs(0.632 μg/mL and 1.150 μg/mL, respectively; P = 0.274) or ATI levels(8.655 AU/mL and 9.017 AU/mL, respectively; P = 0.083).CONCLUSION IFX-TL/ATI levels were well correlated with the clinical activity in South Korean CD patients. Our findings support the usefulness of IFX-TLs/ATI levels in treating CD patients receiving IFX in clinical practice. AIM To investigate the clinical implications of infliximab trough levels (IFX-TLs) and antibodies to infliximab (ATI) levels in Crohn’s disease (CD) patients in Asian countries. METHODS IFX-TL and ATI level were measured using prospectively collected samples obtained with informed consent from CD patients being treated at Asan Medical Center, South Korea. We analyzed the correlations between IFX-TLs / ATI levels and the clinical activity of CD (quiescent vs active disease) based on the CD activity index, C-reactive protein level, and physician’s judgment of patients’ clinical status at enrollment. The impact of concomitant immunomodulators was also investigated. RESULTS This study enrolled 138 patients with CD (84 with quiescent and 54 with active disease). In patients with quiescent and active diseases, the median IFX -TLs were 1.423 μg / mL and 0.163 μg / mL, respectively (P <0.001) and the median ATI levels were 8.064 AU / m L and 11.209 AU / m L, respectively - positive groups, the median IFXTLs were 1.415 μg / mL and 0.141 μg / mL respectively (P <0.001). In patients with and without concomitant immunomodulator use, there were no differences in IFX-TLs (0.632 μg / mL and 1.150 μg / mL, respectively; P = 0.274) or ATI levels (8.655 AU / mL and 9.017 AU / mL, respectively; P = 0.083) .CONCLUSION IFX-TL / ATI levels were well correlated with the clinical activity in South Korean CD patients. findings support the usefulness of IFX-TLs / ATI levels in treating CD patients receiving IFX in clinical practice.