Gorny Altai is one of most active seismic areas of Eurasia. The paper provides data on its historical and instrumental seismicity. The geomorphological effects of the Chuya (Altai) largest-earthquake of 27 September 2003, with Ms = 7.3 and shaking intensity I0 = IX on the MSK 64 scale are considered. The paleoseismic deformations (fault scarps, landslides, and seismites) which are similar of primary and secondary surface deformations of the Chuya earthquake are shown in the Kurai, South Terekta, and Katun fault zones. The signatures of the ancient seismogenic deformations indicate that the three active fault zones generated numerous large earthquakes in the middle Pleisocene-Holocene, which reached moment magnitudes of 6.5 to 7.7 and shaking intensities of IX to XI.
