  The observable consequences of a lowering of the restmasses of vector mesons
on dilepton spectra in the SIS energy regime (HADES) and on photoabsorption
cross sections on nuclei are studied in a transporttheoretical framework. We
also investigate the consequences of a mass-shift of kaons in dense matter and
compare with recent SIS data. The need for a detailed understanding of the
elementary processes is underlined.
