The crystal structure of CoCl 2 ·6H 2 O has been determined by the X-ray single crystal method. The unit cell is monoclinic with a =10.34 Å, b =7.06 Å, c =6.67 Å and β=122°20'. The space group is C 2 h 3 – C 2/ m and the unit cell contains two molecules. Two Cl - ions and four water molecules are octahedrally coordinated to Co 2+ ion to form the group [CoCl 2 ·4H 2 O].These groups are held together parallel to the b axis by O…H–O type hydrogen bonds. The other two water molecules of the formula unit are far from Co 2+ ion. The crystal has the layer structure parallel to (001), and this causes the perfect cleavage. The structure proposed for this salt by Stroganov et al. seems to be incorrect.