The suitability of using10B and5LiF in contact with cellulose acetate butyrate (CAB) for the measurement of slow neutron densities has been investigated. The upper energy threshold of clear Diacel cellulose nitrate (CN) and of the CAB have also been measured. The CAB in good contact with thick10B or5LiF sources offers good promise for the detection of slow neutrons. For the actual CAB samples used, the CAB-10B combination had an efficiency of ∼1.3 × 10−2tracks per thermal neutron incident in a 2π solid angle. The corresponding number for the CAB6-Li combination is ∼5.6 × 10−3tracks per thermal neutron.