1) Inhalable powder containing, 0.04 to 0.8% of tiotropium in admixture with a physiologically acceptable excipient, characterised in that the excipient consists of a mixture of coarser excipient with an average particle size of 15 to 80 mum and finer excipient with an average particle size of 1 to 9 mum, the proportion of finer excipient constituting 1 to 20% of the total amount of excipient. 2) Inhalable powder according to claim 1, characterised in that the tiotropium is present in the form of the chloride, bromide, iodide, methanesulphonate, paratoluenesulphonate or methyl sulphate thereof. 3) Inhalable powder according to claim 1 or 2, characterised in that it contains between 0.048 and 0.96% of tiotropium bromide. 4) Inhalable powder according to one of claims 1 to 3, characterised in that it contains between 0.05 and 1% of tiotropium bromide monohydrate. 5) Inhalable powder according to one of claims 1 to 4, characterised in that the excipient consists of a mixture of coarser excipient with an average particle size of 17 to 50 mum and finer excipient with an average particle size of 2 to 8 mum. 6) Inhalable powder according to one of claims 1 to 5, characterised in that the proportion of finer excipient in the total amount of excipient is 3 to 15%. 7) Inhalable powder according to one of claims 1 to 6, characterised in that the tiotropium salt used has a mean particle size of 0.5 to 10 mum. 8) Inhalable powder according to one of claims 1 to 7, characterised in that monosaccharides, disaccharides, oligo- and polysaccharides, polyalcohols, salts or mixtures of these excipients with one another are used as the excipients. 9) Inhalable powder according to claim 8, characterised in that glucose, arabinose, lactose, saccharose, maltose, dextrane, sorbitol, mannitol, xylitol, sodium chloride, calcium carbonate or mixtures of these excipients with one another are used as the excipients. 10) Inhalable powder according to claim 9, characterised in that glucose or lactose or mixtures of these excipients with one another are used as the excipients. 11) Process for preparing the powders for inhalation according to one of claims 1 to 10. characterised in that in a first step the coarser excipient fractions are mixed with the finer excipient fractions and in a subsequent step the excipient mixture thus obtained is mixed with the tiotropium salt. 12) Inhalable powder according to one of claims 1 to 10 which may be obtained according to claim 11. 13) Use of an inhalable powder according to one of claims 1 to 10 or according to claim 12 as a medicament. 14) Use of an inhalable powder according to one of claims 1 to 10 or according to claim 12 for preparing a pharmaceutical composition for treating diseases in which tiotropium salts may provide a therapeutic benefit. 15) Use according to claim 14 for preparing a pharmaceutical composition for treating asthma or COPD. 16) Use of an inhalable powder according to one of claims 1 to 10 or according to claim 12 for preparing a capsule (inhalette). 17) Capsule (inhalette), characterised in that it contains from 3 to 10 mg of powder for inhalation according to one of claims 1 to 10 or according to claim 12. 18) Capsule (inhalette) according to claim 15, characterised in that it contains between 1.2 and 80 mug of tiotropium.