The M & S configuration gives equilibrium for a toroidal plasma without net current in the azimuthal direction and without rotational transform. Explicit solutions are obtained only for the restricted cases β=0, and β ≦ 1 in the surface current model, but configurations with continuous pressure profile are proved to exist. The use of the M & S configuration to confine a toroidal theta pinch plasma leads to problems in the establishment of the equilibrium and in particular in its stability. The stability of the M & S configuration is investigated for the simplified case of the corrugated linear theta pinch. LIMPUS. This configuration is theoretically unstable with respect to m ≧ 1 flutes. Mechanisms to suppress these modes are based on finite gyroradii stabilisation for m ≧ 2. and on the conducting wall for m = 1, the latter case being limited to very high β. No m 2 instabilities are observed experimentally, although m = 1 instabilities with growth times agreeing with MHD theory are detected. An extrapolation of these results to an M & S configuration gives τ m&s /τ D ≈ (ξ 0 /τ D ) 1/2 where τ D is the average minor radius, ξ 0 an initial deviation from the M & S equilibrium position, and τ M&S and τ D are the M & S confinement time and the toroidal drift time, respectively. M&S experiments with theta pinch plasmas near 10 eV, τ m&S is extended by a factor 3 - 4 beyond τ D , which is in agreement with the above relation. This suggest firstly, that the M & S configurations investigated are an adequate approximation to the required equilibrium, and, secondly, that the MHD instabilities substantially limit the confinement time. Simple models show that oscillating axial currents, a steady axial motion of the LIMPUS magnetic field configuration or a standing wave like oscillation can suppress the instabilities mentioned. Experiments on such dynamic stabilisation are in progress.