The present invention provides pyrazolo[3,4-d]-pyrimidines of the general formula: ##STR1## wherein R.sub.1 is a C.sub.1 to C.sub.6 -alkyl radical, a C.sub.2 to C.sub.6 -alkenyl radical, a C.sub.3 to C.sub.7 -cycloalkyl radical or an aryl radical, R.sub.2 is a C.sub.2 to C.sub.6 -alkenyl radical, a C.sub.3 to C.sub.7 -cycloalkyl radical or an aralkyl or hetaralkyl radical with 1 to 6 carbon atoms in the alkyl moiety and substituted, if desired, one or more times by halogen, C.sub.1 to C.sub.6 -alkyl, hydroxyl, C.sub.1 to C.sub.6 -alkoxy, C.sub.1 to C.sub.3 -haloalkyl, C.sub.3 to C.sub.7 -alkoxy carbonyl, aminocarbonyl, C.sub.2 to C.sub.7 -alkylaminocarbonyl, C.sub.3 to C.sub.13 -dialkylaminocarbonyl, cyano or C.sub.1 to C.sub.6 -alkylthio and R.sub.3 is a hydrogen atom or a C.sub.2 to C.sub.6 -alkyl radical substituted, if desired, one or more times by hydroxyl or is a tetrahydrofuranyl or tetrahydropyranyl radical, with the proviso that R.sub.2 cannot be an unsubstituted benzyl radical when R.sub.1 is a methyl radical, and the physiologically acceptable salts thereof with inorganic and organic acids.The present invention also provides processes for the preparation of these compounds and pharmaceutical compositions containing them.