Theoretical research on coordinated multi-point (CoMP) in the cellular uplink claims large improvements in spectral efficiency and fairness. However, the real-world implementation of CoMP is linked with major challenges such as multi-cell synchronization and multi-cell channel estimation, which have to be addressed to make sure that CoMP finds its way into next generation cellular systems (e.g. LTE-Advanced). In this paper, we provide a proof-of-concept that uplink CoMP concepts do in fact yield significant spectral efficiency gains in an outdoor deployment of two cooperating base stations and two terminals. We further show that the performance gains of CoMP in various interference scenarios corresponds quite well with predictions from theory.