Cancer studies frequently employ clinical endpoints for outcome reporting in order to estimate treatment effect sizes. Most often these outcome assessments use time‐to‐event measures in addition to tumour response, toxicity and quality of life (QOL). The Kaplan‐Meier method is often used to estimate the actuarial rate for time‐to‐event measures. Non‐stratified or stratified log‐rank tests are frequently applied assessing the treatment effect among groups. The Cox proportional hazards regression model is commonly used to estimate the hazard ratio between different treatments. Because cancer outcome is often confounded by multiple other outcomes (e.g. various causes of death), competing risks regression models are used to assess the treatment effect. In addition, intermediary endpoints, such as changes in tumour size, tumour‐related chemical markers and tumour metabolism may also assist in evaluating new treatments. Therefore, the ability to accurately and reliably assess the direct antitumour effect of investigational therapies is critical for the optimal conduct of clinical trials. The goal of this chapter is to summarize general principles of cancer outcome reporting and estimation of treatment effect, and response assessment.