Abstract Difference in the drilling concept between wells planned for underground storage purposes and those for crude oil or gas are discussed. The completed wells are investigated by means of a series of logs to analyse the quantitative mineral composition of the salt. The method avoids most of the expensive core drilling. The results gained by the computer-calculated interpretation of the log have been confirmed by observations made during the leaching process. The well-known mineral composition enable the planning of a detailed leaching program for every envisaged cavern. It contains among other things the number of washing stages in every cavern, the intervals for sonar logging and the time required to create the desired volume. Together with a description of the technical installations used a report on experiences with material and equipment is given. The performance and supervision of the leaching process is discussed, especially the different methods to determine the cavern volume created. It has been found that, depending on the shape of the cavern, major differences in volume sometimes occur due to the different calculation methods used. To enable permanent control of shape development of the cavity during the leaching process, a procedure has been introduced using the field data obtained. Introduction For many years storage caverns for natural gas and LPG in salt deposits have been built and used, especially in USA. In Germany the first cavern for seasonal storage of butane with a capacity of about 125,000 bbls. was completed in 1963. In recent years an ever increasing number of caverns have been planned and built for storing crude oil or fuel oil. Especially since several European countries have promulgated laws obligating petroleum refiners to maintain petroleum stocks, a growing interest in this type of storage has become apparent. In case of favorable geological and topographical conditions storage in caverns is superior to all other methods from an economic standpoint. Since 1968 various projects for creating storage capacity to meet the stockpiling obligation are under construction in North Germany. In the following the storage project of Sottorf near Hamburg serves as an example to report on experience gained and methods used during the construction of this project.