Efficient neutron counters have been constructed using large area layers of a mixture of lithium fluoride and zinc sulphide, the scintillation light being transmitted to photomultipliers by wavelength shifting light guides. An array of these counters has been assembled to form a neutron multiplicity detector for use in a superheavy element search. This array had a detection efficiency for fission neutrons of 37+or-2% and a neutron diffusion time of 83 mu s. The measured background rate of the array, when operated underground at a depth of 60 mwe, was 0.36+or-0.02 s^-1.