In this paper we consider a second-order Sturm-Liouville-type boundary value operator of the formon an arbitrary, bounded time-scale T, for suitable functions p, q, together with suitable boundary conditions. Operators of this type on time-scales have normally been considered in a setting involving Banach spaces of continuous functions on T. In this paper we introduce a space L 2 (T) of square-integrable functions on T, and Sobolev-type spaces H n (T), n 1, consisting of L 2 (T) functions with nth-order generalised L 2 (T)-type derivatives. We prove some basic functional analytic results for these spaces, and then formulate the operator L in this setting. In particular, we allow p ∈ H 1 (T), while q ∈ L 2 (T) -this generalises the usual conditions that p ∈ C 1 rd (T κ ), q ∈ C 0 rd (T κ 2 ). We give some immediate applications of the functional analytic results to L, such as 'positivity', injectivity, invertibility and compactness of the inverse. We also construct a Green's function for L. The analogues of these results on real intervals are well known, and are fundamental to the usual Sturm-Liouville theory on such intervals.