We report differential conductance measurements through a double quantum dot with adjustable interdot tunneling rate. The Coulomb gap of the double dot decreases continuously as the interdot tunnel conductanceGintis increased, from the gap of two isolated dots (whenGint∼0)to the gap of a single large dot of twice the total capacitance (whenGint=2e2/h).Excited electronic states in differential conductance measurements on single dots show a spectrum which is essentially independent of the number of electrons in the dot, but is not uniform. ©1997 American Institute of Physics.