A fast-neutral power of up to 570 kW has been injected into TFR. At low densities (e ≅ 2–3 × 1013 cm−3), the central ion temperature was doubled to 2 keV as a result of the injection. The ion temperature increases linearly with the injected power. Macroscopic perturbations due to the injected power yield information on the ion behaviour and the ion energy confinement time. There are indications, that the ion heat conduction might be anomalous. Effects of neutral injection on equilibrium, stability, and impurity concentration are discussed.