We present results for the dc conductance, the ac conductance, and the current–current fluctuation spectra of mesoscopic, phase-coherent conductors based on a second quantization approach to scattering and a self-consistent potential approach. A second quantization approach permits an investigation of statistical effects due to the symmetry of the wave functions under exchange of particles. A self-consistent approach is needed to enforce overall charge conservation and to obtain current conserving expressions for frequency-dependent conductances and fluctuation spectra. For the particular example of a mesoscopic capacitor we present microscopic expressions for the electrochemical capacitance and the charge relaxation resistance.