This chapter continues the discussion begun in Chapter 4 by considering the third of the three questions employment tribunals must address when faced with an unfair dismissal claim: Did the employer act reasonably in carrying out the dismissal? If the answer is ‘yes’, then the dismissal is fair, if it is ‘no’, then it is unfair and the issue of an appropriate remedy is considered by the tribunal. The chapter explores this concept of ‘reasonableness’ in detail. It explains how it has evolved over the decades and why its interpretation by the courts remains highly controversial. In particular, it focuses on how the courts have determined what does and what does not constitute a fair dismissal on grounds of misconduct, poor performance and ill health.