Summary of the study. In a genome-wide association study (GWAS) of 1037 Canadians with cystic fibrosis (CF), we found two novel loci linked to chronic Pseudomonas aeruginosa infection age. We found evidence of a shared polygenic component and a potential causal relationship between chronic P. aeruginosa infection and lung disease. ^#: the rs62369766 locus was validated using an independent French cohort (n=501).