Inthe years 1976-1978 3,552 strains of Shigella sonnei obtained from the whole Czechoslovak territory by the method of colicin typing and phage typing was examined. Each strain represented always one focus. 81.3% of the strains were colicinogenic. Twenty-one colicin types, 41 characteristic and 105 non-characteristic phage types participated in bacillary dysentery. Of the total number, 77.4% belonged to 9 phage types (2, 3, 6, 65, 67, 75, NC IV-VIII- and NC III-IV-VIII-), which are endemic in Czechoslovakia. Of the 2,889 colicinogenic strains, 85% belonged to 3 colicin types: 2 = Ia (31%), 6/11 = E1 (27%), 12 = E6 (27%). Some phage types produced predominantly colicin of a certain type.