Abstract. We present a preconditioned nullspace method for the numerical solution of large sparse linear systems that arise from discretizations of continuum models for the orientational properties of liquid crystals. The approach effectively deals with pointwise unit-vector constraints, which are prevalent in such models. The indefinite, saddle-point nature of such problems, which can arise from either or both of two sources (pointwise unit-vector constraints, coupled electric fields), is illustrated. Both analytical and numerical results are given for a model problem.Key words. nullspace method, liquid crystals, saddle-point problems, unit-vector constraints AMS subject classifications. 65F08, 65F10, 65F50, 65H10, 65N22 DOI. 10.1137/120870219 1. Introduction. Many continuum models for the orientational properties of liquid crystals involve one or more state variables that are vector fields of unit length. The pointwise unit-vector constraints associated with discretizations of such models give rise to indefinite linear systems of saddle-point form, when these constraints are imposed via Lagrange multipliers. In problems such as these, indefiniteness also frequently manifests itself due to another influence (coupling with applied electric fields), and this leads to a double saddle-point structure. We are interested in the efficient numerical solution by iterative methods of large sparse linear systems of algebraic equations associated with such problems. We begin by presenting some background on these materials and models.