The 'Spheromak', an optimal force-free spherical plasma configuration, is analysed for its MHD stability properties. It is shown that flattened ellipse (oblimak) with = k (k independent of ) should be stable against all magnetically driven MHD and resistive tearing modes if surrounded by a conducting wall at about rw/r0 = 1.15. β's of at least 2% can be stably confined, equivalent to 20% in tokamaks.