Topological separability is crucial for the utility representation of a complete preference relation. When preferences are incomplete, this axiom has suitably de...ned counterparts: upper separability and lower separability (Ok (2002)). We consider the problem of representing an incomplete preference relation by means of a vector-valued utility function; we obtain representation results under the lower separability assumption. Our results extend the main representation theorems by Ok (2002) in terms of the separability axioms.