Novel bicyclic condensed pyrimidine compounds having general formula (I) ##STR1## wherein X is --CH.sub.2 --, --NH--(CH.sub.2).sub.n --, --O--(CH.sub.2).sub.n -- or --S--(CH.sub.2).sub.n -- in which n is zero or 1; A is a 4,5-fused imidazole ring N-substituted by R.sub.3 which is hydrogen, C.sub.1 -C.sub.4 alkyl or benzyl, or A is a 2,3-fused pyridine ring C-substituted by R.sub.4 which is hydrogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, halogen or NR.sub.5 R.sub.6 in which each of R.sub.5 and R.sub.6 independently is H or C.sub.1 -C.sub.4 alkyl; B is a bicyclic ring chosen from tetralin, indane and 2-oxindole; each of R.sub.1 and R.sub.2 independently is hydrogen, C.sub.1 -C.sub.4 alkyl, halogen, hydroxy, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 alkoxycarbonyl, nitro, cyano or CF.sub.3 ; and the pharmaceutically acceptable salts thereof.