P-Cresol is an end product of protein breakdown and also it is a fermentation metabolite of tyrosine. The mechanisms underlying colonic carbohydrate and protein fermentation, responsible for the generation of p-cresol, are only partially understood. After absorption, the majority of p-cresol is conjugated to form p-cresyl sulphate. There is clear evidence, both in vitro and in vivo, that accumulation of conjugated fermentation metabolites is correlated with clinical important endpoints. In renal failure, the colonic generation rate of p-cresol is markedly elevated. Free p-cresol is an independent predictor for mortality in hemodialysis patients. The accumulation of p-cresol increases the cardiovascular risk of chronic kidney disease (CKD) patients. It was shown, that p-cresol l triggered autophagic renal proximal tubular cells death via JNK-mediated p62 accumulation and then activated caspase 8-dependent cell death pathway. Thus p-cresol can be considered as one of the key events causing progression of CKD, which might affect drug disposition in CKD cases.