A Study of Atezolizumab in Combination With Carboplatin or Cisplatin + Pemetrexed Compared With Carboplatin or Cisplatin + Pemetrexed in Participants Who Are Chemotherapy-Naive and Have Stage IV Non-Squamous Non-Small Cell Lung Cancer (NSCLC) (IMpower 132)

Inclusion Criteria:

• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
• Histologically or cytologically confirmed, Stage IV non-squamous NSCLC. Participantswith tumors of mixed non-small cell histology (i.e., squamous and non-squamous) areeligible if the major histological component appears to be non-squamous
• No prior treatment for Stage IV non-squamous NSCLC. Participants with a sensitizingmutation in the epidermal growth factor receptor (EGFR) gene or with an anaplasticlymphoma kinase (ALK) fusion oncogene are excluded. Participants with unknown EGFR andALK status require test results at screening from a local or central laboratory
• Participants who have received prior neo-adjuvant, radiotherapy, adjuvantchemotherapy, or chemoradiotherapy with curative intent for non-metastatic diseasemust have experienced a treatment-free interval of at least 6 months fromrandomization since the last dose of chemotherapy and/or radiotherapy
• Participants should submit a pre-treatment tumor tissue sample if available before orwithin 4 weeks after enrollment. If tumor tissue is not available, participants arestill eligible
• For participants enrolled in the extended China enrollment phase: current resident ofmainland China, Hong Kong, or Taiwan and of Chinese ancestry
• Measurable disease, as defined by RECIST v1.1
• Adequate hematologic and end organ function
• For women of childbearing potential: agreement to remain abstinent or usecontraceptive methods that result in a failure rate of less than (<) 1 percent (%) peryear during the treatment period and for at least 5 months after the last dose ofatezolizumab or 6 months after the last dose of cisplatin
• For men: agreement to remain abstinent or use contraceptive measures and agreement torefrain from donating sperm

Exclusion Criteria: Cancer-Specific Exclusions

• Participants with a sensitizing mutation in the EGFR gene or an ALK fusion oncogene
• Active or untreated central nervous system (CNS) metastases as determined by computedtomography (CT) or magnetic resonance imaging (MRI) evaluation during screening andprior radiographic assessments
• Spinal cord compression not definitively treated with surgery and/or radiation orpreviously diagnosed and treated spinal cord compression without evidence that diseasehas been clinically stable for greater than or equal to (>= 2) weeks prior torandomization
• Leptomeningeal disease
• Uncontrolled tumor-related pain
• Uncontrolled or symptomatic hypercalcemia (greater than [>] 1.5 millimole/Literionized calcium or calcium >12 milligrams/deciliter or corrected serum calcium >upperlimit of normal)
• Malignancies other than NSCLC within 5 years prior to randomization
• Known tumor programmed death-ligand 1 (PD-L1) expression status from other clinicalstudies (e.g., participants whose PD-L1 expression status was determined duringscreening for entry into a study with anti-PD-1 or anti-PD L1 antibodies but were noteligible are excluded) General Medical Exclusions:
• History of severe allergic, anaphylactic, or other hypersensitivity reactions tochimeric or humanized antibodies or fusion proteins
• History of certain autoimmune disease
• History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-inducedpneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis
• All participants will be tested for human immunodeficiency virus (HIV) prior to theinclusion into the study and HIV-positive participants will be excluded from theclinical study
• Severe infections within 4 weeks prior to randomization
• Significant cardiovascular disease, such as New York Heart Association cardiac disease (Class II or greater), myocardial infarction or cerebrovascular accident within 3months prior to randomization, unstable arrhythmias, or unstable angina
• Illness or condition that may interfere with a participant's capacity to understand,follow, and/or comply with study procedures Exclusion Criteria Related to Medications and Chemotherapy:
• Prior treatment with EGFR inhibitors or ALK inhibitors
• Any approved anti-cancer therapy, including hormonal therapy within 21 days prior toinitiation of study treatment
• Prior treatment with cluster of differentiation 137 (CD137) agonists or immunecheckpoint blockade therapies, anti-PD-1, and anti-PD-L1 therapeutic antibodies
• Treatment with systemic immunostimulatory agents within 4 weeks prior to randomization
• Treatment with systemic immunosuppressive medications Exclusion Criteria Related to Chemotherapy:
• History of allergic reactions to cisplatin, carboplatin, or other platinum-containingcompounds
• Participants with hearing impairment (cisplatin)
• Grade >=2 peripheral neuropathy as defined by National Cancer Institute CommonTerminology Criteria for Adverse Events (NCI CTCAE) version 4.0 criteria (cisplatin)
• Creatinine clearance (CRCL) <60 milliliters/minute (mL/min) for cisplatin or <45mL/min for carboplatin