Experimental techniques previously used for measuring neutron spectra in fast critical assemblies have been applied to reactor shielding problems. Fast-neutron spectra in the energy range from 25 keV to 1 MeV have been measured in the water shield surrounding a small thermal research reactor. Three different water thicknesses were investigated, as well as a combination of water with a 2-in.-thick slab of iron. The spectrometer system developed for these measurements employs small proton-recoil proportional counters, together with electronic pulse-shape discrimination for the rejection of gamma-ray signals. Since this discrimination is extremely important for shielding measurements, the detectors and electronic system are described in some detail. The basic theory underlying proton-recoil measurements of neutron spectra is reviewed, as well as the techniques used to correct for errors arising due to finite detector size and irregularities in the electric field within the counters. Results of the water measurements indicate that the spectrometer is capable of measuring the absolute neutron flux as well as relative variations within the spectrum at a given point. In addition, predictions of spectral hardening with increasing water thickness are verified. The water-iron measurements indicate that the system is capable of measuring spectral features caused by resonances in the cross section of the shield material.