Reasonableness as a concept used in determining delictual liability or liability in tort law, is either embraced or perceived by some as frustrating. It is a normative concept which is inextricably linked with the concepts of fairness, justice, equity, public policy and the values of the community. These concepts assist in providing value judgements in determining liability. It is apparent from this study that the influence of reasonableness is predominantly implicit on the French law of delict, but more explicit on the South African law of delict and Anglo-American tort law. Its influence varies with respect to each element of tort or delictual liability. In order to hold a person liable for a delict or tort, it is only reasonable that all the elements of a delict or tort are present. Common to all the jurisdictions studied in this thesis is the idea of striking a balance between the defendant’s interests promoted, the plaintiff’s interests adversely affected and the interests of society. Where liability is based on fault, the reasonableness of conduct is called into question. In respect of causation whichever test or theory is used, what must ultimately be determined is whether according to the facts of the case, it is reasonable to impute liability on the defendant for the factually caused consequences. Whether loss or harm is required, assumed or not required, the question of the appropriate remedy or compensation which is reasonable under the circumstances is called into question. In South African and Anglo-American law, the multiple uses of the standards of the reasonable person, reasonable foreseeability of harm, reasonable preventability of harm, whether it is reasonable to impose an element of liability, or whether it is reasonable to impute liability, often cause confusion and uncertainty. At times, the role of these criteria with regard to a specific element may be valid and amplified while, at other times, their role is diminished and controversial. However, there is nothing wrong with the concept of reasonableness itself; indeed, it is a necessary and useful concept in law. Rather, it is the way that it is interpreted and applied in determining liability that is problematic. / Private Law / LL. D.