SAKAMATA is a risk assessment and mitigation tool developed by TNO and used by the Royal Netherlands Navy. It supports the user in planning and carrying out active sonar operations in an environmentally responsible way. Recently, a new version has been developed, which makes it possible to quantify the number of marine mammals affected, taking into account physical injury, temporary hearing impairment and behavioural disturbance. Also, the efficacy of possible mitigation measures, such as variation of the sonar parameters, ramp-up schemes or alternative operation areas are quantified and presented to the operator. In SAKAMATA a scenario can be defined by positioning a platform on a map and selecting a sonar. A marine mammal database provides information on all marine mammals present at that time of year. Environmental information is taken from a database or specified manually by the user. An exposure assessment is carried out based on these input parameters, sound propagation as computed by the ALMOST model, and a model of behavioural response of marine mammals to sonar. This paper provides an overview of the exposure and risk assessment framework, and the underlying models and assumptions. Possible mitigation strategies that can be adopted will be demonstrated.