Pyrimidine derivatives of the formula (I) and physiologically acceptable
salts thereof, in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, W, X, Y and Z
are as defined in claim 1, exhibit phosphodiesterase V inhibition and can
be employed for the treatment of diseases of the cardiovascular system
and for the treatment and/or therapy of potency disorders ##STR00001##