To continue our investigation of the epidemiology of giant cell arteritis (GCA) in southern Europe, we assessed the potential presence of trends, peaks, and fluctuations in the incidence of this vasculitis over a 25-year period in the Lugo region of northwestern Spain. We also sought to determine whether changes in the clinical spectrum of the disease existed. From 1981 to 2005, biopsy-proven GCA was diagnosed in 255 Lugo residents. The age- and sex-adjusted annual incidence rate was 10.13 (95% confidence interval [CI], 8.93-11.46) per 100,000 population aged 50 years and older. The mean age +/- SD at the time of diagnosis was 75.0 +/- 6.9 years. The annual incidence rate in women (10.23; 95% CI, 8.60-12.08) was slightly greater than that in men (9.92; 95% CI, 8.19-11.89) (p = 0.15). The annual incidence rate increased with advancing age up to a maximum of 23.16 (95% CI, 19.52-27.28) in the 70-79 year age-group. A progressive increase in the incidence was observed from 1981 through 2000 (p = 0.001). However, the age- and sex-adjusted incidence rate for biopsy-proven GCA in the Lugo region did not show peaks in the annual incidence of GCA. Likewise, we observed no seasonal pattern for the diagnosis of the disease. Visual ischemic manifestations and irreversible visual loss were observed in 57 (22.4%) and 32 (12.5%) of the 255 patients, respectively. A negative trend manifested by a progressive decline in the number of patients with visual ischemic manifestations (p = 0.021) or permanent visual loss (p = 0.018) was found over the 25-year period of study. The decline in the frequency of visual manifestations of GCA could not be attributed to a shorter delay to diagnosis, as no significant differences were observed when the delays to diagnosis in the 5 consecutive 5-year periods were compared. In conclusion, the current study confirms a progressive increase in the incidence of biopsy-proven GCA in northwestern Spain, and suggests that there has been a change in the clinical spectrum of the disease.