Anti-TNF-α therapy, such as infliximab (IFX), has profoundly changed treatment to induce and maintain remission for inflammatory bowel diseases patients who do not respond to conventional therapies. Unfortunately, IFX, as a chimeric protein, is potentially immunogenic, and antibodies to infliximab (ATI) may interfere with the pharmacodynamics and pharmacokinetics of the drug, thus resulting in a loss of response for a substantial proportion of patients. The clinical efficacy of IFX is correlated with the levels of IFX and ATI. Therefore, monitoring patients for the trough levels of IFX and the presence of ATI is very important. The procedures and characteristics of six assays for monitoring IFX and ATI are described in this review, and the comparisons between them are also discussed. To date, there has been no optimal assay for monitoring IFX and ATI. Therefore, many technical problems need to be solved to make therapeutic drug and immunogenicity monitoring a part of routine clinical management. .