Human health and the quality of the environment are threatened by the amount of harmful substances in soil. Risks that contaminated sites pose to our health and the environment have to be assessed, and the ones that are found to be unacceptable need to be managed. This chapter summarizes the basic principles of assessing risks related with contaminated sites. Risk assessment is a part of a process called risk analysis that consists of a step-wise evaluation of a site in order to determine whether it is contaminated or not, if risks exist, and if remediation to reduce those risks is required. After a comparison and judgment of the significance of the risk is done, identification, selection, and implementation of proper actions to control the identified risks are performed (so-called risk management). All parts of risk analysis and management require competent specialists to implement the objective risk assessment and to clearly communicate the message to stakeholders. This is often associated with time-consuming and costly procedures. But if done properly, it can promote the most sustainable options for management of contaminated sites and actually save resources in the long term.