The present invention relates to a crystalline, enantiomerically pure hydrate of R-6-hydroxy-8-{1-hydroxy-2-[2-(4-methoxy-phenyl)-1,1-dimethyl-ethylamino]-ethyl}-4H-benzo[1,4]oxazin-3-one-hydrochloride of formula (1) and its activity as a long-acting betamimetic, on its own or combined with one or more other active substances for treating respiratory complaints.
