Bossy and autocratic superiors. Non-managers – lax, lazy or unassertive in their work. Difficult personalities, piggy-backers, bullies and avengers – the styles of work behavior are many. Neglect of client needs, maltreatment and maximisation of personal benefit. Unresolved conflicts. The problems are prevalent and familiar. Why is nothing done about them? The answer is the Evil Eleven Syndrome. The book describes the dark side of workplaces, weakening both wellbeing and performance. The theoretical frame of reference is the X Efficiency theory of organisational economics. With the help of this innovative theory it is possible to explain, conceptualise and understand phenomena that traditional economic theory does not address. The book examines organisational inefficiency from the perspective of human decision-making, work behaviour and pressures. The individual level is important, because organisational performance is based on the productivity of work. The book provides cross-disciplinary, interesting and practical reading for researchers, supervisors, developers and trainers, as well as anyone working in an organisation.