The study presents phytosociological and ecological data from azonal black alder forest sites in the southern part of central Slovakia. A data set of 29 relevés was collected by authors in vegetation season 2010 following the standard Braun-Blanquet approach. Numerical classification was performed to delimit the main vegetation types, while statistical analyses were applied to explain the vegetation-environmental relationships. Three associations within two classes were distinguished using a TWINSPAN algorithm.