The applicability and usefulness of k0-based reactor neutron activation analysis (NAA) in the life sciences is evaluated from the following examples: 1. Instrumental NAA of NIST SRM 1633a coal fly ash, as a quality assessment; 2. Radiochemical NAA of Versieck's reference human serum, and--herewith associated--the development of practical correction procedures for neutron-induced reaction interferences and of improved methods to evaluate the detection efficiency and the correction for true coincidence; and 3. Determination of the lanthanides in plant leaves and lichens near a Portuguese coal-fired power station, which led to the introduction of the Westcott formalism and to the use of a low-energy photon detector. As concluded, k0-based NAA is at present capable of tackling a large variety of analytical problems when it comes to the multielement determination in environmental and biological matrices.