MarNIS is a project that is sponsored by DGTREN of the European Union. MarNIS deals with safety and efficiency at sea and in ports. This paper is a result of the investigations of MarNIS in risk. It tries to describe risk in ports and the way in which this risk may be mitigated. The paper starts with an overview of the project MarNIS. MarNIS consists of 5 clusters: Information management, new technologies, Vessel Traffic Management at sea, Vessel Traffic Management in ports, and Safety and Logistic Information Management on board. The cluster Vessel Traffic Management in ports consists of 'Modern VTS' and the use of information flows on board vessels. Risk of a vessel is an important issue for the harbourmaster. If the risk is excessive he should determine whether or not to allow the vessel to enter and in what way he might reduce risk to safeguard the facilities in the port as well as to keep the access to the port free of obstacles. The paper discusses the establishment of VTS based on modern technology and is dependent on the way in which the risk of vessels during navigation can be reduced by VTS. The paper discusses a number of methods that are used to determine risk and the way in which these risks are mitigated.