Background and Aims. Vitamin D deficiency is a major health problem worldwide, especially in the elderly, so that an accurate assessment of its prevalence is essential for planning reliable healthcare policy throughout the lifespan. The aim of the present study was to assess the concentration as well as the mild and moderate deficiencies of 25-hydroxyvitamin D (25OHD) across different ages and genders. Methods. We searched the database of the local Laboratory Information System to retrieve results of 25OHD tests performed on the whole cohort of presumably healthy Caucasian outpatients aged >12 yrs, who were referred to our laboratory in the North-East of Italy for routine laboratory testing ordered by general practitioners, over a 3-year period (October 2008 - October 2011). Results. Cumulative results for 25OHD testing were retrieved for 2327 outpatients (1744 females and 583 males). No significant differences between females and males were observed for 25OHD values (71 [25-140] versus 67 [27-130] nmol/L; p=0.40), as well as a similar prevalence of mild (32.8 versus 33.4%; p=0.89) and moderate (21.7 versus 25.6%; p=0.37) 25OHD deficiency. A non significant variation of 25OHD values was also found by ANOVA analysis throughout four age cohorts (<21, 21-40, 41-60 and >60 yrs), in both genders. In each age group, the values of 25OHD did not significantly differ between genders. The percentage of subjects displaying mild and moderate 25OHD deficiencies in the older subgroup was comparable to that observed in the younger adult population. Conclusions. The results of this large epidemiological investigation attest that the prevalence of mild and moderate vitamin D deficiency does not significantly increase with aging and seems lower than that observed in other European and American countries.