Industrial communication often has to work in an environment where other networks or radiation create different levels of interference for the data traffic. Additionally, industrial applications often demand predictable real-time performance of the network. One way of trying to utilise the available frequencies in an effective manner is to include cognitive functionality in the network. We present a medium access control protocol for a cognitive radio network, providing deterministic medium access for heterogeneous traffic and dynamic spectrum allocation. Spectrum sensing abilities in the nodes open up for the possibility of increasing successful data transmissions, and a real-time analysis framework provides upper-bounded medium access delay in order to guarantee timely treatment of hard real-time traffic. © 2012 IEEE.