A disruption is a termination of a Tokamak discharge after a sudden loss of stability or confinement. Because of the fast time scale in which the plasma thermal and electromagnetic energy are dissipated, these events lead to large thermal loads on in-vessel components and strong electromagnetic forces on surrounding conductors. Especially in larger tokamaks, like JET, disruptions have been able to cause considerable damage and in order to preserve the integrity of the device it is therefore important to prevent or mitigate such events. Hence it is important to limit the number of disruptions during the operational life-time of the device. For ITER operations at high current the disruption rate should be 1% or less. It is therefore useful to study what the rate of disruptions in present day, large, Tokamaks, like JET is. Here the disruption rate is defined as the fraction of discharges that disrupt. Previously disruption rates of various devices have been reported to be in the order of 20-40%, significantly higher than those aimed for ITER operations. Another, even more useful, parameter that can be determined is the disruptivity of specific plasmas, i.e. the likelihood that plasmas in a specific state will disrupt. At JET a dedicated database has been maintained, recording each disruption during the operational life. Using this database a statistical analysis of the occurrence of disruptions at JET has been carried out to obtain the overall disruption rate of JET [3]. Furthermore, trends in the disruption rate can be determined. These results will be presented in the first section of this paper. In section 3 the disruptivity as function of various plasma parameters will be presented. Here we focussed mainly on the three main operational boundaries of Tokamak operations, i.e. the low-q limit, the density or Greenwald limit and the b or Troyon limit. In section 5 the statistics of the JET disruption prevention system are presented followed by a concluding section.