As the therapeutic landscape in haematological malignancies has evolved from traditional chemotherapies to novel biological, targeted, and cellular therapies, adverse event profiles have accordingly shifted with emerging and newly described chronic, cumulative, and delayed symptomatic adverse events. The current standard of toxicity reporting in clinical trials, centred on maximum-grade adverse events, is wholly inadequate for characterising the tolerability of therapies in the modern era. As such, the science of adverse event measurement, analysis, and reporting in clinical trials needs to evolve with our ever-growing repertoire of therapeutics to facilitate more comprehensive and accurate toxicity assessment for treatment decision making.