The karyotypes and sex chromosome systems of the four European species of noterid beetles are described. Chromosome preparations were made from the mid-gut and testes of adult beetles by acetic acid spreading. Canthydrus diophthalmus was found to have a chromosome compliment of 2n = 16 + XX/XY. A multiple sex chromosome system was common to the three species of Noterus investigated (2n = 18 + X1X1X2X2/X1X2Y). The behaviour of Noterus sex chromosomes during early meiosis was examined and is discussed, along with the occurrence of multiple sex chromosome systems in other Adephaga.