A pyrimidine derivative of formula (I) wherein, for example, R.sup.1 is hydrogen, (1 6C)alkyl, (3 5C)alkenyl or (3 5C)alkynyl; Q.sub.1 and Q.sub.2 are independently selected from phenyl, naphthyl, indanyl and 1,2,3,4-tetrahydronaphthyl; and one or both of Q.sub.1 and Q.sub.2 bears on any available carbon atom one substituent of formula (Ia) [provided that when present in Q.sub.1 the substituent of formula (Ia) is not adjacent to the --NH-- link]; wherein, for example, X is CH.sub.2, O, S or NH; Y is H or as defined for Z; Z is OH, SH, NH.sub.2, (1 4C)alkoxy, (1 4C)alkylthio, --NH(1 C)alkyl, --N[(1 4C)alkyl].sub.2 or --NH--(3 8C)cycloalkyl; n is 1, 2 or 3; m is 1, 2 or 3; and Q.sub.1 and Q.sub.2 may optionally bear other substituents selected, for example, from halogeno, (1 6C)alkyl, cyano and (2 4C)alkenyl; or a pharmaceutically-acceptable salt or in-vivo-hydrolyzable ester thereof; are useful as anti-cancer agents; and processes for heir manufacture and pharmaceutical compositions containing them are described ##STR00001##