  We study the Coulomb blockade in a chaotic quantum dot connected to a lead by
a single channel at nearly perfect transmission. We take into account quantum
fluctuations of the dot charge and a finite level spacing for electron states
within the dot. Mesoscopic fluctuations of thermodynamic and transport
properties in the Coulomb blockade regime exist at any transmission
coefficient. In contrast to the previous theories, we show that by virtue of
these mesoscopic fluctuations, the Coulomb blockade is not destroyed completely
even at perfect transmission. The oscillatory dependence of all the observable
characteristics on the gate voltage is preserved, its period is still defined
by the charge of a single electron. However, phases of those oscillations are
random; because of the randomness, the Coulomb blockade shows up not in the
averages but in the correlation functions of the fluctuating observables (e.g.,
capacitance or tunneling conductance). This phenomenon may be called
"mesoscopic charge quantization".
