A new species, Fridericia dissimilis n. sp., found during a study of the aquatic oligochaete fauna in the region of [math]nie[math]nik Massive (Sudety Mts, south-western Poland) is described. The species belongs to the Fridericia group of species characterised by asymmetrical spermathecae with a single diverticulum, but it is easily distinguished from other species by, the enormous size of the gland at the ectal orifice of the spermatheca and the shape of ampulla, andby the shape of the brain and seminal vesicles.