Muon catalysed d-t fusion has been suggested as a possible means for producing high yields of 14MeV neutrons. As an example we mention the proposal by Petitjean et al. [123]. In the muon catalysed fusion process, negative muons are captured on the lower Bohr orbit of deuterium or tritium atoms. The muon’s orbit radius is around 2.5 fermis, close to the nuclear radius, so that the Coulomb field of the deuteron (or triton) is almost cancelled. The probability of fusion of the muon accompanied deuteron or triton with another t or d nucleus becomes large. After fusion, most often, the muon is shaken out and becomes available for another cycle until it decays or is captured by a heavy nucleus. It has been found that up to 150 fusions per muon can be obtained. According to Petitjean et al. the optimum beam-target combination for negative pion, and thus negative muon, production is a beam of 1.5 GeV deuterons impinging on a carbon target. The HETC [92] simulation gives a maximum negative pion yield of 0.16. It follows that the maximum possible number of produced 14MeV neutrons per GeV of deuteron is around 15. These neutrons could be further multiplied by (n, 2n), and even (n, 3n), reactions. A multi­plication factor of 2 seems a maximum. Finally we see that no more than 30 neutrons per GeV-deuteron can be produced. Since not all muons will be captured by the heavy hydrogen atoms, a maximum number of 15 is more likely. This is a factor of 2 below the neutron yield from protons on uranium. Note the advantage that the pion production target can be completely disconnected from the neutron source. However, the (d, t) cell requires high pressures, and a high magnetic field is necessary to trap and focus the muons. It is doubtful that this technique could be used competitively.