New imidazotriazolopyrimidine derivatives of the formula Preferred are those compounds wherein: R1 denotes methyl, which is optionally substituted by phenyloxy or pyrrole; or R1 denotes benzyl which is optionally substituted by hydroxy, methoxy, dimethylaminoethoxy or fluorine; or R1 denotes cyclopentyl, furan or phenylethyl; R2 or R3 denote ethyl, n-propyl, allyl or propargyl; R4 or R6 denote hydrogen; and, R5 denotes methyl, n-propyl, tert.butyl, cyclopentyl or norbornenyl. These are adenosine antagonists are are useful for, inter alia, the treatment of senile dementia of the Alzheimer's type.