Abstract.In an effort to extend the theory of algebraic geometry over groups beyond free groups, Duncan, Kazatchkov and Remeslennikov have studied the notion of centraliser dimension for free partially commutative groups. In this paper we consider the centraliser dimension of free partially commutative nilpotent groups of class 2, showing that a free partially commutative nilpotent group of class 2 with non-commutation graph has the same centraliser dimension as the free partially commutative group represented by the non-commutation graph .2000 Mathematics Subject Classification. Primary 20F18; 20F36. Introduction.There has been much interest in recent years in the development of algebraic geometry over groups (see [1, 10, 12]), inspired by various successes in the study of equations over groups, such as Makanin's algorithm for deciding whether a system of equations over a free group has a solution, and the solution of Tarski's problem concerning the elementary theory of free groups by Kharlampovich and Myasnikov [9], and, independently, Sela [16]. In [3], Chiswell and Remeslennikov showed that if V is an irreducible algebraic set defined by a one-variable system of equations over a non-abelian free group, F, then either V = F, or V is a point, or there exist elements f, g, h ∈ F such that V = f C F (g)h, where C F (g) is the centraliser in F of g. It is therefore believed that the investigation of the structure of the centraliser lattice of a group is a first step in the construction of algebraic geometry over that group. The centraliser dimension of a group is defined to be the height of its centraliser lattice, a concept which has been studied in numerous papers, for example [15], [11], [2], [13] and [4]. To extend the theory of algebraic geometry over groups beyond free groups, Duncan, Kazatchkov and Remeslennikov [5] have studied the notion of centraliser dimension for free partially commutative groups, also known as graph groups, trace groups or right-angle Artin groups.Given an arbitrary variety of groups, V, we may define the class of free partially commutative V groups in an obvious fashion. In this paper we consider the centraliser dimension of free partially commutative nilpotent groups of class 2. We begin, in Section 3, by considering the form of powers and roots of group elements. We then investigate the structure of centralisers in free partially commutative nilpotent groups of class 2 in Section 4. In Section 5 we show that to calculate centraliser dimension in these groups we only need to consider chains of centralisers of generating elements. This result is then used to show that a free partially commutative nilpotent group of class 2 with non-commutation graph has the same centraliser dimension as the free partially commutative group represented by non-commutation graph .