Aryl- and heteroarylethenylene derivatives of formula ##STR1## wherein Y is a mono- or bicyclic ring system chosen from (A), (B), (C), (D), (E), (F) and (G) ##STR2## R is a group of formula R.sub.1 is hydrogen, C.sub.1 -C.sub.6 alkyl or C.sub.2 -C.sub.6 alkanoyl; R.sub.2 is hydrogen, halogen, cyano or C.sub.1 -C.sub.6 alkyl;n is zero or an integer of 1 to 3: n is zero or an integer of 1 to 3 when Y is a ring system (A); it is zero, 1 or 2 when Y is a ring system (B), (E), (F) or (G); or it is zero or 1 when Y is a ring system (C) or (D); and the pharmaceutically acceptable salts thereof; and wherein each of the substituents R, OR.sub.1 and R.sub.2 may be independently on either of the aryl or heteroaryl moieties of the bicyclic ring system (A), (E), (F) and (G), whereas only the benzene moiety may be substituted in the bicyclic ring system (B), are useful as tyrosine kinase activity inhibitors.