Objective. To examine whether giant cell arteritis (GCA) is associated with increased all-cause mortality and whether mortality differs according to age, sex, and calendar year of cohort entry. Methods. Using the UK-based Clinical Practice Research Datalink, we identified 9,778 newly diagnosed GCA patients from 1990-2014, and up to 10 nonvasculitis patients randomly matched to each case on age, sex, practice, and years of history before cohort entry. We used Cox regression to estimate adjusted hazard ratios (HRs) for mortality of GCA patients in comparison to nonvasculitis patients, then stratified by age, sex, and calendar year of cohort entry. Results. Compared with nonvasculitis patients, GCA patients had increased mortality during the first year following diagnosis (adjusted HR 1.51, 95% confidence interval [95% CI] 1.40-1.64), and marginally increased mortality between 1 and 5 years after the diagnosis (adjusted HR 1.16, 95% CI 1.09-1.23), but not >5 years after the diagnosis (adjusted HR 1.06, 95% CI 1.00-1.12). GCA patients diagnosed before age 65 years had the highest mortality risk during the first year following diagnosis (adjusted HR 2.32, 95% CI 1.60-3.35). The mortality risk did not differ substantially by sex or calendar year of cohort entry. Conclusion. GCA patients had an increased risk of mortality during the period shortly after the GCA diagnosis, in particular during the first year, but no increased risk after 5 years postdiagnosis. The mortality risk differed by age with an even greater increased 1-year mortality in those age <65 years at diagnosis, but not by sex or calendar year of cohort entry. 1