This paper analyses the potential effects of commercial banks' expansion in
to the securities business in the context of the contemporary theory of fin
ancial intermediation. The analysis focuses on the gains claimed to emerge
with that expansion, particularly the gains due to information advantages a
nd economies of scope, and on the costs also claimed to arise with it; name
ly, those due to conflicts of interest and safety and soundness considerati
ons. The paper ends with a discussion on how these effects depend on the lo
cation of the securities unit within the banking conglomerate.