Admixtures of albuterol with ipratropium and/or cromolyn, of albuterol and budesonide, or tobramycin, or colistin are physico-chemically compatible. Physico-chemical compatibility has been demonstrated for admixtures of cromolyn with albuterol and/or ipratropium and for admixtures of cromolyn and budesonide. Admixtures of budesonide with ipratropium and/or fenoterol, and admixtures of budesonide and albuterol, or cromolyn are physico-chemically compatible. Both cromolyn and colistin are incompatible with benzalkonium chloride. Admixtures should be prepared from inhalation solutions/suspensions formulated without preservatives.