This study provides a comprehensive review of the current state of knowledge regarding the effects of compressed working weeks on a broad range of outcomes, including: productivity and job performance; absenteeism and turnover; sleep and recovery periods; safety in the workplace; occupational health; and workers’ job satisfaction, attitudes, and preferences. The paper also considers a variety of factors that can affect these outcomes, including potential differences between industrialized and developing countries. It concludes that, while there are clearly increased risks to health and safety associated with compressed workweeks, even with the use of longer (e.g. 12-hour) shifts these potential risks can often be reduced considerably if these shifts are properly structured and include adequate rest periods. Towards that objective, the paper also provides a set of practical recommendations regarding how to implement compressed workweeks to counter fatigue and improve performance.