 Examples are provided by taking formula_2 to be an imaginary quadratic field, formula_43 and formula_44 where formula_45 is the ring of integers of formula_2 (for example formula_47 and formula_48).The groups thus obtained are the Bianchi groups.They are not cocompact, and any arithmetic Kleinian group which is not commensurable to a conjugate of a Bianchi group is cocompact.