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 a single endothermic event at about 191-3°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 <； 10µ. The cocrystal is also disclosed for use as medicament, in particular for the treatment of a respiratory complaint, such as chronic obstructive pulmonary disease (COPD), bronchitis, emphysema and asthma. A pharmaceutical composition comprising the cocrystal as active ingredient is also disclosed, in particular for administration by inhalation. In the latter case, said cocrystal has a mean particle size of 0.5 to 10 µm, preferably 1 to 6 µm, more preferably 1.5 to 5 µm.
