Inclusion Criteria:  Body weight >=30 kg at baseline for participants between >=12 and <18 years of age. Physician confirmed diagnosis of moderate to severe atopic dermatitis at the time of enrollment. Upadacitinib initiated as per the local label. The decision to prescribe upadacitinib must have been made prior to and independently of study participation. Medical and medication history available at least for the last 6 months.  Exclusion Criteria:  - Current participation in interventional research (note: this does not include non-interventional, post-marketing observational studies, or registry participation).