Weyl semimetals contain an even number of singular points in their Brillouin zone around which the dispersion is linear and the density of states (DoS) vanishes. How does the density of states change in the (inevitable) presence of impurities? This question has been the subject of an intensive and partially controversial discussion in the recent literature. In particular, it has been suggested that below a critical disorder strength the DoS remains zero, and that the system supports a phase transition separating an intrinsically clean from a disordered phase. In this talk, I discuss this problem on the basis of several effective models. All these support the integrity of the Weyl node and hence are compatible with the above scenario. I will also comment on the (tricky) comparison to numerics and point out a puzzle whose solution invites mathematical research.