Background: Lung cancer is the leading cause of cancer death in Taiwan. The poor prognosis of lung cancer patients with advanced disease and recent development of precision medicine motivates the investigation of molecular targets. The purpose of the study is to estimate the prevalence of KRAS gene mutations and 15 other gene targets among non-small cell lung cancer (NSCLC) patients in Taiwan. Methods: This retrospective study included 933 NSCLC patients diagnosed between January 1992 and July 2018 at six medical centers in Taiwan, including Taichung Veteran’s General Hospital, Chung San Medical University Hospital, China Medical University Hospital, Kaohsiung Veteran’s General Hospital, Tri-Service General Hospital and National Taiwan University Hospital. Patients ≥18 years, had primary histologically confirmed NSCLC diagnosis at time before any treatment, and availability of archival tumor tissue with >30% tumor cellularity. Mutational Analysis: The Formalin-Fixed Paraffin-Embedded (FFPE) tumor blocks were analyzed for the prevalence of somatic mutations. The entire coding sequence of 16 genes was analyzed by next generation sequencing of macrodissected DNA from FFPE recut slides at a depth of greater than 300x and interrogated for somatic pathogenic variants. RNA was not available; hence this limits sensitivity to detect fusions. Results: The mean age at diagnosis was 62 years, 498/933 (53%) were women, 411/843 (49%) were smokers or former smokers, and 829/933 (89%) of adenocarcinoma histopathology. Stage was available for 723 patients with a distribution of 328/723 (45%) Stage I, 120/723 (17%) Stage II, 210/723 (29%) Stage III, and 65/723 (9%) Stage IV. EGFR mutations were identified in 327/933 (35.1%) and TP53 mutations in 179/933 (19.2%). KRAS mutations were identified in 72/933 (7.7%) patients, with KRAS G12C mutations observed in 23/933 (2.5%), KRAS G12D in 16/933 (1.7%), and KRAS G12V in 14/933 (1.5%) (Table). In addition, co-occurring mutations with KRAS were observed and are highlighted, including 14 TP53, 4 PIK3CA, 2 EGFR, 2 CTNNB1, 1 STK11, 1 BRAF and 1 PTEN. Conclusions: EGFR and TP53 were the most frequent mutations identified among all stage NSCLC in Taiwanese populations, followed by KRAS. KRAS G12C and KRAS G12D, the two most frequent KRAS mutations, were identified in 32% and 22% of the KRAS-mutant tumors. Although the prevalence of any KRAS mutation or KRAS G12C mutation is lower than typically seen in Western countries, it is similar to observations among Asian populations. These findings broaden the understanding of the mutational landscape of NSCLC patients in Taiwan to inform development of new therapeutic approaches.