The detection of special elements that can be used by terrorists in improvised chemical weapons can be performed by the spectroscopic analysis of neutron-induced gamma rays. Numerical simulations and experiments have been performed with the aim of designing a portable inspection system. Both thermal neutron analysis (TNA) and the associated particle technique (APT) have been studied within French CBNRE (chemical, biological, nuclear, radiological and explosive) R&D program. The results obtained so far show that TNA and APT can be used in complement to reach the largest possible panel of detectable elements.