A trust can be broken in two ways: by stepping outside the powers altogether, or by exercising them while falling short of the duties they carry. This chapter opens with the nature of the personal claim, how it differs from a proprietary one, and the objective that drives quantification. It then identifies who can be sued — joint and several liability among co-trustees, liability through passivity, and the position of retiring and newly appointed trustees. Finally it works through the accounting techniques of falsification and surcharge, the bar on setting off gains against losses, and the distinctive approach to causation and interest in these claims.