OBJECTIVES:  Programmed death-ligand 1 (PD-L1) is an immune-related biomarker expressed on different tumor cells of different tumor types, including non-small cell lung cancer (NSCLC). Because of the availability of PD-L1 inhibitor therapies, testing for the PD-L1 biomarker has become common practice in clinical settings. The objective of this study was to determine the factors associated with patients being tested across several countries. METHODS:  A multi-country retrospective medical chart-review of NSCLC patients was conducted by cancer-treating physicians in the United States (N=7,334), 5EU (France, Germany, Italy, Spain, UK; N=16,549), and Japan (N=3,492) between Q2 2015 and Q1 2016. Physicians randomly selected patient charts currently on an anti-cancer regimen and abstracted data on patient demographics, disease status, treatment patterns, and biomarker status. Logistic regression models were conducted to predict testing status from patient history and physician characteristics. RESULTS:  A total of 20,575 patients were included (63.9% male; mean age=64.7 years); 20.7% received a PD-L1 test. Testing was most common in Germany (36.1%) and least common in Japan (1.92%). Tested patients were younger, had higher ECOG scores, and more likely to be male, a current smoker, treated by a hematologist/oncologist, and treated in a university/teaching hospital (all p<.05). Logistic regression results suggested the strongest predictors of testing were being in Germany (odds ratio [OR] = 4.28), stage at diagnosis (stages IIc [OR=3.02] and III [OR=4.08] were more likely to be tested than stage IV), and higher ECOG scores (score of 4 vs. 0: OR=5.41; score of 3 vs. 0: OR=2.92) (all p<.05). CONCLUSIONS:  As immuno-oncology therapies, such as a PD-L1 inhibitors, become more common, biomarker testing will continue to play an important role in clinical practice. The results suggest significant variability across countries for PD-1L testing among NSCLC patients, with performance status and staging being more predictive of patient testing than physician setting or specialty.