Cryptogenic epilepsy, accounting for ~40% of adult-onset epilepsies and a lesser proportion in paediatrics, is defined as epilepsy of presumed symptomatic nature in which the cause has not been identified. It has a higher prevalence of refractory seizures when compared to those with idiopathic epilepsy (40 vs. 26%). These patients are usually treated with multiple anti-epileptic drugs, yet the total number of which used is inversely proportional to their efficacy. Moreover, these children may have significantly worse behavioural problems and can result in substantial cognitive impairments when older. Luckily, the number of cryptogenic epilepsy cases is diminishing due to better diagnostic abilities in recent years. We aim to divide this chapter into three parts. First, we hope to discuss our working algorithm and explain the use and advantages of different imaging modalities including high-field 3-Tesla MRI with morphological analysis for accurate localisation of the epileptogenic foci. We shall then elaborate the concept of the epileptogenic circuit and explore the selection criteria for more invasive approaches, such as depth electrodes and SEEG. Last but not the least, we aim to discuss the surgical treatments, including VNS and DBS, and their outcomes in these patients.