A cocrystal of tiotropium bromide and lactose monohydrate is herein disclosed. In the cocrystal the components tiotropium bromide and lactose are preferably present in an almost stoichiometric ratio. Said cocrystal has a single endothermic event at about 191-193° C. determined by DSC. A process for the preparation of the cocrystal is also disclosed. Preferably, the cocrystal has a particle size distribution of D90