The photochemical behaviour of a new series of bisanthracenes in fluid solution and in polymer matrices is described. These systems which incorporate an acetal link undergo an efficient photocycloisomerization. Moreover, new polymers bearing anthracene pendant groups were described; they undergo at 366 nm an interchain anthracene photodimerization with a twofold increase of their average molecular weight (($) over bar M(w)). Photodissociation easily proceeds at 270-280 nm in solution as well as in polymers.