This is an observational, multicenter study in participants treated with nivolumab for the approved indications of melanoma and Lung cancer in Australia, the EU, Switzerland, the United Kingdom (UK), and the United States (US). The targeted countries in the EU for study participation include Austria, Belgium, Czech Republic, France, Germany, Hungary, Italy, Poland, and Spain. Study objectives are to assess the safety experience, survival, adverse event management, and outcomes of adverse events associated with nivolumab in routine oncology care facilities.

Inclusion Criteria:

• Age ≥18
• Histologically or cytologically confirmed diagnosis of melanoma (including uveal melanoma) or lung cancer
• Treatment with commercial nivolumab for the first time, alone or in combination with ipilimumab, for the approved indications of nivolumab within 14 days before informed consent for this study OR in the case where treatment has not yet been initiated, documentation that the treatment strategy is determined before an informed consent to study participation, and treatment is initiated within 28 days after informed consent

Exclusion Criteria:

• Prior participation in a clinical trial within the past 4 weeks
• Previously treated with anti-PD-1, anti-PD-L1, or anti-PD-L2 antibodies
• Previously treated with anti-CTLA-4 for lung cancer
• Current or pending participation in a clinical trial
• Current or pending systemic treatment for cancer other than melanoma and lung cancer
• Inability to comply with the study protocol

The study population consists of 417 adults treated with nivolumab for histologically or cytologically confirmed melanoma and 772 adults treated with nivolumab for histologically or cytologically confirmed lung cancer in accordance with the approved indications in Australia, the EU, Switzerland, the UK, and the US. The targeted countries in the EU for participant enrollment include Austria, Belgium, Czech Republic, France, Germany, Hungary, Italy, Poland, and Spain. Participants who begin treatment with nivolumab for the first time will be enrolled in accordance with the approved indications and whose treatment strategy was determined independently from consideration of study participation. Treatment will be determined at the treating physician's discretion and with the participant's consent.