Background: Aristolochic acids (AA) form carcinogenic DNA adducts, which can be detected in human urinary tract (kidney, ureter, and urinary bladder), liver, and non-target tissues such as pancreas, breast, and lung. AA is blamed for urothelial carcinoma (UC) but its carcinogenic role on lung cancer is still under debate. This study plans to investigate the characteristics of double cancers with urothelial carcinoma and lung adenocarcinoma (LA). Methods: We conducted this multi-institutional cohort study in Taiwan. Two independent cohorts were retrieved from Chang-Gung Research Database (CGRD). The first cohort (UCLA) included patients with double cancers with urothelial carcinoma (UC) and lung adenocarcinoma (LA) from 1994 to 2023 and the second cohort (CGMH-EGFRm) with EGFR-mutated LA from 2011 to 2020. UCLA was further divided into groups according to the sequence of cancer development (group 1: index diagnosis date of UC before LA; group 2: simultaneous LA and UC; group 3:LA before UC), and CGMH-EGFRm was divided into activating EGFR-mutations (group 4) and other mutations (group 5). The last follow-up time was Dec 30, 2023. Descriptive statistics are provided with Chi-Squared and Fisher's Exact Test. P<0.05 was set to be statistic significance.Results: From 1994 to 2023, cohort 1 comprised of 196 patients of which 126 in group 1, 30 in group 2, and 40 in group 3 and from 2011 to 2020 cohort 2 comprised of 3,427 patients. The last follow-up time was Dec 30, 2023, and the mean age of group 1, 2, and 3 was 73, 73, and 67, respectively. The male gender in group 1, 2, and 3 was 65.9%, 66.7%, and 67.5%, and smoking habit was 30.2%, 26.7%, and 42.5%, respectively. The baseline characteristics such as age, gender, smoking habits were different from group 1 to 5, while in UCLA cohort, gender and smoking habits were similar. The median interval of diagnosis between double cancer was 2381.5 (range: 131 to 10556), 8.5 (0 to 84) and 755.5 (98 to 4390) days, respectively. After 2000s (based on year of diagnosis with UC), there was an increasing trend in group 2 and 3. The anatomical locations of LA was similar between groups 1 to 3 (p=0.660), and a trend of increasing renal pelvis and ureter UC in group 3 (p=0.104). Conclusion: 1.1% of UC can develop LA in CGRD. Further genomic analysis between groups was warranted to elucidate the carcinogenic role of AA in double cancers.