The arthropods in abandoned nests of the Sand Martin in two localities in South Slovakia are analysed. They are represented mostly by species penetrating into the nests from the immediate surroundings more or less occasionally, or seeking a suitable cover for wintering there. There are three abundant components of the nest fauna with a close relation to the nests: the mites represented by the species Hypoaspis lubrica, Androlaelaps casalis and Dermanyssus hirundinis, fleas represented almost exclusively by Ceratophyllus styx and predators represented by the only species Haplglossa nidicola. The abundance of mites and fleas on one hand and of Haplglossa nidicola on the other hand exhibits the typical features of the predator/prey relationship, in the individual nests and in time. All major groups of the nest fauna exhibit two abundance maxima in the winter period.