Rare b -> s μ+ μ– transitions that proceed via flavour changing neutral currents are suppressed in the SM and provide a sensitive probe of new physics contributions entering in competing diagrams. The dataset collected with the LHCb experiment has enabled measurements to be made in decays such as B0 -> K*0 μ+ μ–, B+ -> K+ μ+ μ– and B0s -> φ μ+ μ–. Particularly interesting are the angular and isospin asymmetries in the decay B0 -> K(*)0 μ+ μ–, which are sensitive probes of new physics. The large statistics of reconstructed B mesons allow, for the first time, experimental access to b -> d μ+ μ– transitions, such as B+ -> π+ μ+ μ–, which are further suppressed in the SM. The latest results on these decay modes will be presented.