Ionosphere is an ionized layer of atmosphere and affects radio signals due to its variable electron density. Total Electron Content (TEC) and Slant Electron Content (STEC) is a measure of the ionizing of the electrons along a ray path in the ionosphere. STEC values of the ionosphere can be estimated by IONOLAB-TEC method. During extreme ionospheric storms gradients becomes larger than those of quiet days since time delays of the radio signals becomes anomalous. In this study, ionospheric gradients over Turkey are estimated using the Turkish National Permanent GPS Network (TNPGN-Active) between May 2009 and September 2012. GPS-STEC for each station is calculated using IONOLAB-TEC and IONOLAB-BIAS methods (www.ionolab.org). Significant variations in the structure of station-pair gradients have been observed depending on location of station-pairs, the path of the satellites, strength of the geomagnetic storms and type, depth and magnitude of the earthquakes.