Abstract: A human or animal subject having a solid tumour is treated by administering to the subject therapeutically effective amounts of a nitric oxide (NO) synthase inhibitor and a compound which is an imidazole or 1,2,4-triazole derivative of formula (A) ##STR1## wherein X is selected from the group consisting of ##STR2## wherein R is hydrogen or a C.sub.1 -C.sub.6 alkyl group; each of R'.sub.1 to R'.sub.5 is independently selected from the group consisting of hydrogen, C.sub.1 -C.sub.6 alkyl, hydroxy(C.sub.1 -C.sub.6 alkyl), phenyl, (C.sub.1 -C.sub.6 alkyl)phenyl and phenyl(C.sub.1 -C.sub.6 alkyl); m is 0 or 1; n is 1 or 2; and Z' represents a leaving group which has the potential for expulsion via an intramolecular cyclisation reaction and which is not negatively-charged; or a physiologically acceptable acid addition salt thereof.