Historical buildings, which have survived throughout history to the present, are exposed to a rapid corrosion process due to natural effects, misuse and conscious destruction. The only way to ensure their survival without losing their characteristics is to adopt the right measures which will result in conscientious restorations. The main problem with restoration of buildings that have suffered from different effects is to find building materials to repair the structural damage and material decay. The repair techniques must match the original materials used in the building. Information determined about the original materials in buildings is very important in order to choosing the restoration materials. After general evaluation, it is necessary to determine what restoration materials can match the original mortars in both form and structure. General principles of restoration, include conserving the original construction materials and techniques as much as possible and preserving a building’s authenticity by choosing techniques which will not harm the building’s essential historical structure were used during initial construction. For this reason, it is very important to carefully determine what original materials and to prepare a matching restoration material that will not alter the building’s originality. Many mistakes have been seen especially with materials and building techniques used in most of the restorations in Turkey. The recent restorations, in particular with a few exceptions, have damage buildings because conscientious approaches, where not employed. These hasty restorations have caused both a loss of information about past technologies and materials used in construction, and they have destroyed the historical value of these buildings. One of the most damaging effects of these abovenamed restorations is the use of materials incompatible with the historical features of the building without having performed necessary analyses. Many studies have analyzed the corrosion process and the structure of mortars used to connect natural stones which were preferred due to their aesthetics, variety and strength in traditional buildings all along the history of monumental constructions. However, when we consider that every district and every period has its own particular of construction materials, it is clearly seen that these studies have not yet become widespread, especially in Anatolia. Although some studies have been conducted on puzzolanas (volcanic ashes which are used to improve hydraulic features), it is necessary to expand these studies in order to be certain that these materials are appropriate for different districts and different time periods. The purpose of this thesis is to design the recipes of repair mortars and plasters for the conservation works in Kayseri which has a great potential of volcanic materials and tradition of hydraulic mortars. In this context, fifteen buildings in Kayseri belonging to the Roman, Byzantine (4th, 6th, 11th century), Seljuk (13th, 14th century) and Ottoman (15th, 16th, 18th, 19th century) periods have been selected for sampling. The original mix proportions and properties of the samples have been identified by physical, chemical, mechanical and petrographical analysis and classified according to their similar properties. Evaluating these analyses, plaster samples which are appropriate for restorations of the overmentioned buildings were designed. In this process, the existing sources for raw materials have been researched; samples from the reactive aggregates, lime kilns and the stone quarries of the region have been searched and evaluated to determine the material that has the similar properties with the original. Conservation mortars have been produced in laboratory medium using the same ratio of mixture determined through the characterization study. Three types of conservation mortars and two types of plasters were tested for their mechanical and physical qualities during six months and these values were compared with original samples