Abstract: A composition comprising microspheres of a polymer matrix, having two different pharmaceutical actives having complementary, usually synergistic, activity in killing cells. The compositions have particular utility for treating tumours. Useful combinations are doxorubicin with rapamycin, irinotecan with ibuprofen, ibuprofen with doxorubicin and irinotecan with doxorubicin. The polymer matrix is preferably a crosslinked polyvinyl alcohol. The drugs may be included in the same microsphere, or microspheres each with an individual pharmaceutical agent may be mixed together. The microspheres are preferably used in chemoembolisation of tumours.