The confinement time on the ST Tokamak was proportional to the plasma current and density and reached values of 10–20 ms near the disruption limit. The confinement showed the effect of neoclassical, single-particle behaviour for non-axisymmetry. The Spitzer conductivity was found by considering Zeff from measured impurities. Runaway electron production was classical, the cross-field transport anomalous. The MHD modes, internal (sawtooth) and major disruptions, and island structures for the m = 2 modes were analysed by soft-X-ray imaging techniques. Ion-cyclotron heating at second-harmonic operation increased the plasma temperature by 100 eV.