OBJECTIVE : Describe the longitudinal development of crowding and patient/emergency department (ED) characteristics at a Swedish University Hospital. METHODS : A retrospective longitudinal registry study based on all ED visits with adult patients during 2009-2016 (N = 1,063,806). Patient characteristics and measures of ED crowding (ED occupancy ratio, length-of-stay [LOS], patients/clinician's ratios) were extracted from the hospital's electronic health record. Non-parametric analyses were conducted. RESULTS : The proportion of unstable patients (triage level 1-2) increased while the proportion of admitted patients decreased. All crowding variables were stable, except for LOS, which increased by 9 min/visit/year (95% CI: 8.8-9.1). LOS for visits by patients ≥ 80 years increased more compared to those 18-79 (248 min vs. 190 min, p < 0.001). Unstable patients increased their median LOS compared to stable patients (triage level 3-5). LOS for discharged patients increased with an average of 7.7 min/year (95% CI: 7.5-7.9) compared to 15.5 min/year (95% CI: 15.2-15.8) for those being admitted. CONCLUSIONS : Fewer admissions, despite an increase of unstable patients, is likely related to lack of in-hospital beds and contributes to ED crowding. The increase in median ED LOS, especially for patients in the subgroups unstable, ≥80 years and admitted to in-hospital care reflects this problem.