Oropharyngeal squamous cell carcinoma (OPSCC) is the most prevalent type of head and neck cancer in men and the second most common type in women in Sweden, with a significant increase in cases since 2005. Despite high survival rates, with a 5-year survival estimated as 72% in Sweden, radiation therapy—a common treatment for OPSCC—often results in xeros-tomia, or xerostomia, due to salivary gland damage. This thesis investigates the incidence, prevalence, and sequelae of hospital-treated radiation-induced xerostomia among OPSCC survivors in Sweden. Utilizing nationwide Swedish registry data, out study sample was comprised of all individuals who had OPSCC from 2000 to 2018 and survived at least two years. We then examined whether survivors who develop xerostomia have higher risks of all-cause mortality, cancer-related mortality, cardiovascular disease, and fractures compared to those who do not develop xerostomia, which was identified by diagnosis recorded during inpatient hospital admission or outpatient clinic visits. Cox regression models were used to derive hazard ratios (HRs) and 95% confidence intervals (CIs), and separate models were fit for each outcome. The study included 2833 OPSCC survivors, among which 68 (2.4%) individuals developed xerostomia between the years 2000 and 2018.. The adjusted hazard ratio for all-cause mortality in xerostomia patients was 1.58 (95% CI: 1.00, 2.50), indicating a significantly increased death risk. However, no significant associations were found for cancer-related mortality, cardiovas- cular disease, or fractures, although there were trends also suggesting increased risk in these outcomes. In conclusion, hospital-treated xerostomia in OPSCC survivors is significantly associated with increased all-cause mortality, highlighting either severe impact of xerostomia on patient health and the necessity for effective treatments, or reversed causation such that those with severe health problems identified their xerostomia during treatments. Further research with larger datasets is essential to validate these findings and explore the potential links between xerostomia and other health outcomes and causality.