An overview is presented of some topics of contemporary focus, mainly in the biological and environmental sciences, and how electron spin resonance (ESR) spectroscopy may aid in their investigation. Specifically considered are: spin-trapping in biological media, the determination of antioxidant efficiencies, the use of nitroxides as probes of activity in cells and of molecular mobility in animal and plant substances, and in materials such as cotton. Further applications involving ESR are shown, as in: radiation dosimetry, dating, studies of zeolites, studies of free radical formation by mechanical stress and by shock-waves from explosions, and for environmental monitoring, e.g. the determination of polyaromatic hydrocarbons (PAH) in the urban atmosphere, of free-radical species in the higher-atmosphere, and in analysing soil samples, humic and other biogenic substances.