Although morbility and mortality in acromegaly are higher than in the general population, there have been very few previous epidemiological studies. This study tries to answer "why". Seventy-four patients affected by acromegaly in Vizcaya (Spain) between 1970 and 1989 were considered for an epidemiological study. The prevalence of known cases at the end of 1989 was 60 per million inhabitants. The average incidence of newly diagnosed cases was 3.1 per million people per year. Unexpectedly, acromegaly was more frequent in women (n = 48) than in men (n = 26), with a ratio of 1.8:1. Mean age at diagnosis was significantly higher in women (46.1 +/- 2.2 yr) than in men (39.5 +/- 2.2 yr) (p < 0.05) There was a positive correlation between age at diagnosis and the estimated duration of the disease (r = 0.56, p < 0.05) and a negative one between age and basal GH serum levels (r = -0.52 p < 0.002). The age at diagnosis was significantly higher in patients with invasive tumors (grade III and IV) than in those with enclosed tumors (grade I and II) (47.7 +/- 1.8 vs 40.1 +/- 3.3 p < 0.05). In general, mortality was higher than the expected for the control population (standardized mortality ratio, SMR = 3.2, 95% confidence interval. Cl = 1.55-5.93). However, mortality was higher in men (SMR = 7, 95% Cl = 2.81-14.4) but not in women (SMR = 1.4 95% Cl = 0.29-4.17).(ABSTRACT TRUNCATED AT 250 WORDS)