OBJECTIVES: Lung cancer is the most common cause of death from cancer worldwide with 1.8 million people diagnosed/year. The disease remains as the most common cancer in men worldwide. The purpose of the article is to evaluate the prevalence of ALK mutations in NSCLC patients in Bulgaria. METHODS: A systematic review of the published data on prevalence of ALK positive NSCLC conducted in other countries and compared to local data, were being carried out. Between January 2016 and June 2016, 132 patients with NSCLC, previously screened for EGFR mutation were selected for ALK mutation analysis. RESULTS: Data is available for 124 patients, for 8 patients tumor mass was insufficient for analysis. ALK mutation was confirmed in 5 patients, 119 patients were diagnosed with ALK wild type. From all ALK positive patients, 3 were with adenocarcinoma, 1 with squamous NSCLC and 1 with other type NSCLC. All ALK mutations were observed in non smoker and ex-smoker patients. ALK mutations were presented only in patients with stage III and IV NSCLC. Histologic examination showed that almost half of the patients were with stage IV NSCLC; 12.9% were with stage III NSCLS; one patient with stage IIa; one with stage IIb NSCLS and two patients with confirmed relapse. Most of the patients were with adenocarcinoma (82 patients), 11 patients were with squamous NSCLC and 2 patients were with other type of NSCLC. CONCLUSIONS: In our study we found that the prevalence of ALK mutation in EGFR negative NSCLC patients is 3.8%.