When the kidney is seriously impaired, various uremic toxins (UTs) accumulate in the body, often exerting unfavorable effects on physiological functions and drug pharmacokinetics. To prevent this, it is important to determine plasma UT levels accurately in chronic kidney disease patients. Although attempts to predict plasma UT levels using biomarkers have been made, the correlation between UT levels and the markers is not yet fully understood. In this study, we assessed the correlations among plasma levels of indoxyl sulfate (IS), indoleacetic acid (IA), and 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (CMPF) in 20 hemodialysis patients and evaluated the relationship between the plasma levels of UTs and clinical parameters, such as serum creatinine (Scr), blood urea nitrogen, and estimated glomerular filtration rate (eGFR), with special focus on IS. There were no correlations among the plasma levels of the three UTs before and immediately after hemodialysis. However, a significant correlation was observed between plasma IS levels and Scr before hemodialysis (r=0.643, p=0.002), with the correlation becoming much stronger when using the data obtained immediately after hemodialysis (r=0.744, p<0.001). Further, plasma IS levels showed a significant negative correlation with eGFR (r=-0.558, p=0.011). However, no correlations were observed for IA or CMPF. The results obtained from this study suggest that plasma IS levels can be predicted from Scr values, although the precise mechanism behind the correlation remains to be clarified.