Extreme conditions are defined in terms of deviation from the norm, and the mismatch between capacity and demand. Analysis of ergonomic job description data revealed the predominance, through their frequent occurrence, of extreme conditions. Extreme work environment conditions, such as climate, acceleration, and air pressure, are discussed. Task and error-concepts for workers operating under extreme workload are investigated, with reference to Chernobyl, stress-strain concepts for ATC, college examinations and shiphandling.