The invention relates to substituted imidazopyridazinediones of general
formula ##STR00001## wherein R.sup.1 to R.sup.4 are defined as in claim
1, the tautomers, the enantiomers, the diastereomers, the mixtures
thereof and the salts thereof, which have valuable pharmacological
properties, particularly an inhibiting effect on the activity of the
enzyme dipeptidylpeptidase-IV (DPP-IV).