The scientific research papers by Professor John William Gorrod who died in December 2015 are reviewed. He was one of the most important scientists in the area and investigated mainly the biological oxidation of nitrogen containing drugs and xenobiotics. In this review, more than 200 papers belong to him are evaluated, most of which involved the results from in vitro microsomal oxidative metabolism of nitrogen containing xenobiotics. These studies include the carcinogenicity of tobacco smoke constituents, aromatic amines, aminophenols, rubber and aminobiphenyls, the assay for ferriheamoglobinemia forming compounds, metabolism of aralkyl azo compounds, aromatic amines, aromatic azaheterocycles, synthesis of N-oxidative metabolites i.e. N-oxides, nitrones and hydroxylamines, mutagenicity of amines, metabolism of adenine derivatives, alicyclic amines and aromatic heterocyclic amines, in vivo and in vitro metabolism of nicotine and related tobacco alkaloids, effects of various substrates on MAO enzyme and reviews related to nicotine and N-oxidation of other nitrogen containing compounds. In the major part of these studies, the spectroscopic and chromatographic methods were developed to evaluate and determine the investigated compounds.