The density and arrangement of dislocations is observed in deformed Cd single crystals by etch pitting. The density versus shear strain curves are given. These curves for crystals oriented for single slip differ from those oriented for double slip. Primary basal screw dislocations seem to prevail in crystals being deformed. For interpretation of the possible interaction of basal dislocations with different 〈112̄0〉 Burgers vectors is taken in account. The plastic behaviour of other h.c.p. metals as revealed by transmission electron microscopy is compared on the basis of the elastic interaction between dislocations with Burger's vector in the (0001) slip plane.