Due to the large number of trace organic compounds (TOrCs) in water and wastewater, their degradation during UV-based advanced oxidation (UV/AOP) is best monitored using a conservative indicator compound. The present study demonstrates the in situ use of sucralose, a widely consumed artificial sweetener, as a conservative probe for UV/AOP degradation of TOrCs. The main qualities of sucralose in this regard are its high concentration in wastewater effluent and surface water (enabling its direct detection), its resistance to direct UV photolysis, and its relatively slow reaction with hydroxyl radical. Degradation of sucralose was compared to the degradation of commonly detected TOrCs, across two AOPs (i.e. UV/H2O2 and UV/NO3), in both lab-scale and pilot-scale systems. In all cases, UV/AOP degradation of sucralose was slower than the degradation of the examined TOrCs, and is expected to be slower than the degradation of the majority of other environmentally relevant TOrCs. These results demonstrate the potential of sucralose as a conservative probe, to monitor the transformation of TOrCs during UV/AOP treatment. Furthermore, degradation of sucralose was slower than the degradation of many transformation products (generated during oxidation of TOrCs), implying that sucralose is also a valuable indicator for the decay of primary transformation products. (C) 2014 Elsevier B.V. All rights reserved.