This paper analyses the time inconsistency problem of both exchange ra
te and fiscal policy in a small open economy. The equilibrium under di
scretion is characterised by inflation and a deficit. Commitment of th
e exchange-rate instrument only, e.g. through membership in a European
monetary union with low inflation, contributes to price stability but
may increase the deficit. Whether the government will prefer this out
come to the discretionary one will depend on the structure of the econ
omy. We conclude that the time-inconsistency argument strengthens the
case for simultaneous commitment of monetary and fiscal policy for inf
lation-prone countries joining a monetary union.