This article reviews the design and operation of a transportable neutron spectrometer. Four of these instruments were produced and have been widely used for applications such as the assessment and classification of radiation hazards at field sites in the United Kingdom and Europe. An overview of the instrument hardware is presented, together with a description of the six sensor channels, their associated processing electronics and the host data logger computer. Spectral unfolding is also summarized and a sample spectra, which was measured from outside a fuel flask, is given. © 2001 American Institute of Physics.