Cisplatin (CisP) is a chemotherapeutic agent used to treat head and neck and lung cancer in adults and over 15 different pediatric cancers. Despite its known toxicity, CisP is still widely used as a first line chemotherapy as it is so effective. Nephrotoxicity is one of the most common adverse effects of CisP, occurring in 20-50% of patients. It manifests as acute kidney injury (AKI) typically within the first few days of exposure and is associated with short and long-term morbidity. Furthermore, AKI diagnosis is only possible once kidney damage has progressed to functional impairment, when mitigation strategies are ineffective. Tests that could predict AKI risk pre-emptively or diagnose early-stage AKI before functional loss would be very impactful, affording opportunities for prevention or early intervention to mitigate CisP nephrotoxicity, reduce morbidity and improve health outcomes. The field of metabolomics seeks to identify patterns of small molecules (metabolites) involved in cell or tissue metabolism related to disease states, or patient factors like lifestyle and genetics. Plasma and urine are ideal for sampling the metabolome, which can identify at-risk patients and reveal disease-related changes earlier than existing diagnostic methods do. In CisP-treated children and adults from across Canada, we will identify urine and plasma metabolite profiles a) prior to CisP dosing that predict CisP AKI risk, and b) shortly after dosing to identify early-stage nephrotoxicity, before clinical signs of AKI are detectable. Our identified biomarkers will allow individualization of CisP treatment based on the level of nephrotoxicity risk and the design of trials to mitigate the progression and complications of CisP nephrotoxicity.