Clinicians should possess current knowledge about the prognosis and expected outcome of endodontic treatment, including apical surgery. This knowledge cannot be acquired by indiscriminate review of the many available studies because they vary in the level of evidence they provide. Therefore, seven studies that best comply with methodology criteria defining the levels of evidence were selected and used as the basis of this review. In spite of their methodological consistency, the outcomes reported in these studies still differ considerably, mainly because of differences in inclusion criteria. According to these studies, 37–91% of teeth can be expected to be healed, while up to 33% can still be healing several years after surgery. Importantly, 80–94% of teeth can remain in symptom-free function, even if they are not healed. Several pre-operative factors may influence the outcome of treatment; the outcome may be better in teeth with small lesions and excessively short or long root canal fillings, and it may be poorer in teeth treated surgically for the second time. With regard to intra-operative factors, the choice of the root-end filling material and the quality of the root-end filling may influence the outcome, while the retrograde retreatment procedure clearly offers a better outcome than the standard root-end filling. In summary, the expected outcome of apical surgery is good and therefore, before considering tooth extraction and replacement, apical surgery should be attempted when it is feasible.