Karyological details were studied in males of seven weevil species. The following number of chromosomes were found in individual species: 2n=32, n_=15+Xyp in Gymnetron tetrum (F.) and Gymnetron smreczynski Fremuth, 2n=44, n_=21+Xyp in Cionus tuberculosus (Scop.), 2n=38, n_=18+Xyp in Cionus hortulanus (Geoffr.), Cionus ganglbaueri Wingelm. and Cionus nigritarsis Reitt., 2n=42, n_=20+Xyp in Cionus olivieri Rosensch. In the first meiotic metaphase the heterochromosomes of all the examined species formed a typical parachute bivalent. The chromosome number and sex determining system were described for the first time.