asp b28 human insulin or lys b28 pro b29 human insulin in another preferred embodiment the insulin used is an insulin derivative preferably selected from the group consisting of b29 n u03b5 myristoyl des b30 human insulin b29 n u03b5 palmitoyl des b30 human insulin b29 n u03b5 myristoyl human insulin b29 n u03b5 palmitoyl human insulin b28 n u03b5 myristoyl lys b28 pro b29 human insulin b28 n u03b5 palmitoyl lys b28 u2032 pro b29 human insulin b30 n u03b5 myristoyl thr b29 lys b30 human insulin b30 n u03b5 palmitoyl thr b29 lys b30 human insulin b29 n u03b5 n palmitoyl u03b3 glutamyl des b30 human insulin b29 n u03b5 n lithocholyl u03b3 glutamyl des b30 human insulin b29 n u03b5 u03c9 carboxyheptadecanoyl des b30 human insulin and b29 n u03b5 co carboxyheptadecanoyl human insulin more preferably lys b29 n u03b5 acylated des b30 human insulin the insulin derivatives has a protracted onset of action and may thus compensate the very rapid increase in plasma insulin normally associated with pulmonary delivery by carefully selecting the type of insulin the present invention enables adjustment of the timing and to obtain the desired biological response within a defined time span in order to avoid irritation of the lungs and to eliminate immunological reactions the employed insulin is preferably insulin which has been purified by chromatography such as mc insulin novo single peak insulin e lilly and ri insulin nordisk in a preferred embodiment the zinc free insulin crystals according to the invention further comprise a stabilizing amount of a phenolic compound preferably m cresol or phenol or a mixture of.