This paper introduces a harmonic balance technique in the frequency domain for efficiently determining the harmonic and intermodulation products of nonlinear networks with multi-tone inputs. This eliminates the solution of the system equations in the time domain, conversion from the time domain to the frequency domain (discrete Fourier transform) and reconstruction of the port voltage time domain waveforms from their Fourier series coeffficients as performed in the standard harmonic balance [1],[2],[3].