This invention concerns novel aminopyrimidinium salts of the formula I In which R1 is alkyl, alkenyl, cycloalkyl, phenyl, phenylalkyl, or cycloalkyl-alkyl, one of R2 and R6 is a basic group selected from amino, alkylamino, dialkylamini of up to eight carbon atoms , pyrrolidino, piperidino and morpholino, and the other of R2 and R6 is hydrogen, alkyl, alkenyl, alkoxyalkyl, phenyl, phenylakyl, cycloalkyl or cycloalkyl – alkyl, or both of R2 and R6 are basic group as mentioned above, and R5 is hyrdrogen, (1-4C)alkyl or (3-6C)alkenyl, or R2 Is a basic group as mentioned above, and R5 and R6 together form alkylene or, together with the appendant carbon atom of the pyrimidine ring, complete a benzene ring, R4 is hydrogen, alkyl cycloalkyl-alkyl, alkenyl, alkynyl or phenylalkyl, or R4 is an optionally substitutued alkylene or alkenylene linked to the nitrogen atom of the group Q.A.N, either of which linking groups may thereby completing a ring including two adjacent carbon atoms of Q, the carbon atoms of A and the adjacent nitrogen atom of the group A.N, A, is a direct bond to the group, N(R4) or is alkylene or oxyalkylene, Q is a pyridyl, furyl, thienyl or phenyl moiety and Y is a physiologically acceptable anion, but excluding a number of compounds specified hereinafter, The invention also includes certain closely related anhydro-base derivatives which, like the formula I compounds, possess beneficical effects on the cardiovascular system ( and in particular beneficical effects modulated via the sino-atrial node) also included are pharmaceutical compositions containing the formula I compounds ( or a related anhydro-base) as active ingredient, and processes for the manufacture of the various novel compounds