This is a study of risk perception and a test of a model of perceived risk. A scale measuring fear was factor analyzed and the resulting five fear factors were related to a large number of risk dimensions, both personal and general. Fear was only rather weakly related to perceived risk. Furthermore, perceived risk of two ionizing radiation hazards (nuclear power, X-rays) were investigated in more detail. These risk ratings were modelled on the basis of attitude, risk sensitivity, specific perceived risk of radiation, trust and an extended version of the traditional Psychometric Model, enhanced by the introduction of a factor of Tampering with Nature. It was found that risk perception could be well explained with this approach and the importance of Tampering with Nature, as well as specific perceived risk, were stressed.