The paper deals with a radar 'track before detect' application in a multitarget setting. 'Track before detect' is a method to track weak objects on the basis of raw radar measurements, e.g. the reflected power of the target plus noise. In classical target tracking, the tracking process is performed on the basis of pre-processed measurements that are constructed from the original measurement data every time step. In this way no integration over time takes place and information is lost. The authors give details of a modelling setup and a particle filter based algorithm to deal with a 'multiple target track before detect' situation. Using simulations it is shown that with this method, it is possible to track multiple, closely spaced, weak targets.