This is a Non-interventional Prospective Study. Centres will enroll adult patients with partial onset seizures for whom the clinician has decided to initiate ZNS as an adjunctive therapy prior to the decision to take part in this study. Patients to be enrolled into the study are not sufficiently controlled with one dug licensed for the use of monotherapy in partial onset seizures. Patients will be seen at baseline and then during normal clinical visits at intervals which are appropriate to the typical practice of the treating clinician. Patients will be assessed at baseline and then at least 3 and 6 months after the baseline.

Open-label, Multi-centre, Multi-national Post-marketing, Non-interventional Observational Study

Inclusion Criteria:

• The decision to prescribe ZNS was made by the physician before and independently of his/her decision to include the patient in the study
• Patients treated with one drug licensed for the use as monotherapy in partial onset seizures
• Based on the physician's clinical judgment, the patient seizure activity is not controlled sufficiently with the current monotherapy and it is in the patient's best interest to be prescribed adjunctive ZNS
• Patient was prescribed ZNS no longer than 2 weeks before baseline
• Treatment with ZNS has to be commenced in line with the drug's license and ZNS SmPC (Summary of Product Characteristics)
• Aged 18 years or older
• Capable of understanding the purpose of the study, fully informed and having given written informed consent.

Exclusion Criteria:

• Patients that have started ZNS outside the approved SmPC at enrolment
• Simultaneous participation in an interventional clinical trial and/or taking an investigational drug
• Any form of substance abuse, psychiatric disorder or condition which, in the opinion of the investigator, may complicate communication with the patient.

Adult Patients With Partial Onset Seizures