Investigation of Radio Spectra and Long Term Variability of GHz-Peaked-Spectrum Radio Sources and Candidates at RATAN-600 Mingaliev M.G., Sotnikova Y.V. The study of the instantaneous spectra and long-term variability of GHz-Peaked-Spectrum (GPS) sources and candidates are present. The sample consists of 123 radio sources which are identified as GPS sources from the literature. We used a possibility of RATAN-600 to get instantaneous radio spectra of object in the wide frequency range. The main task of the work was to determine .true. GPS sources among the heterogeneous sources with spectral maximum. We obtained instantaneous spectra of our sample for two epochs . July 2006 and March 2007 at six frequencies: 1.1, 2.3, 4.8, 7.7, 11.2 and 21.7 GHz. Gigahertz-peaked spectrum (GPS) sources are extragalactic radio sources, both galaxies and quasars, characterized by convex continuum spectra peaking in the gigahertz range and steep at high radio frequencies, compactness (~10-100 milliarcsec), low variability and low polarization. The majority of sources which are known as GPS sources in the literature, have only few data points in radio and the determination of the variability and the shape of the simultaneous spectra is inadequate. As a result, the shape of obtained spectra doesn't reflect information about the variability and the physical processes of such objects. The study of the high radio frequency behavior of extragalactic sources is important for ESA.s (European Space Agency) Planck Surveyor mission. Many of the sources classified as GPS sources in the literature and thus thought to be non-variable, can exhibit variability and appear unforeseeable bright at high radio frequencies during the Planck observation.