SigSpec is a new method to compute the significance of the amplitude levels in the frequency domain, based on the false-alarm probability associated with a peak in the amplitude spectrum. The underlying probability density function (PDF) of the amplitude spectrum generated by pure noise may explicitly be derived if treated as frequency and phase-dependent. A comparison of the analytical solution with the results of extensive numerical calculatgions provides excellent agreement. In addition, the SigSpec software has already demonstrated clear advantages compared with the commonly used Fourier methods in various respects. A few examples for ground-based as well as space photometry are presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html