ABSTRACT: The contribution describes the changes in the yields of the groundwater sources at 18 selected springs with predominantly long-term monitoring period, covering the regions of the Slovak mountains. This evaluation has shown that during the monitoring period 1956 - 1994 the average yields of groundwater springs have been roughly steady until the year 1982. The significant decrease of their yield occurred after 1981. This decrease has been appeared at first and dominantly in the southern part of Slovakia, in the Slovak karst and, with some delays, also in the rest of the evaluated regions of Slovakia. Moreover, it has been shown that in most of the evaluated groundwater sources, this decrease had the progressive tendency. This decrease correlates well not only with the decrease of the amount of annual precipitation but also with the changes of the complex of climatic factors, that have effect on the increasing of evapotranspiration. These decreases in the groundwater yields have the negative effect on water management and ecology in the present time. In the case that the phenomena is not according with the dry period but it has the long-term tendency it will have increasing negative effect in the above mentioned sphere in the future.