Background: Vitamin D deficiency is frequently observed in heart failure patients and it has been shown that vitamin D exerts various effects on the heart that may be relevant for the pathogenesis of myocardial diseases. Aims: We aimed to elucidate the largely unknown association of 25-hydroxyvitamin D [25(OH)D] serum levels with echocardiographic measures of left ventricular (LV) structure and function. Material/Subjects and methods: We measured 25(OH)D serum levels and performed standardized LV chocardiograms in 614 persons from a population-based cohort of older men and women. Echocardiographic data were used to calculate LV mass and geometry and for classification of systolic and diastolic dysfunction. To consider the seasonal variations of 25(OH)D levels we categorized our study participants according to season-specific 25(OH)D quartiles. Resuits: LV systolic function, mass and geometry were not significantly associated with 25(OH)D serum levels. In binary logistic regression analyses, the prevalence of LV diastolic dysfunction was significantly higher in the first season-specific 25(OH)D quartile when compared to the fourth quartile [odds ratio 2.32 (95% Cl: 1.42-3.80); p=0.001] but significance was lost after adjustments for age [odds ratio 1.51 (0.89-2.57); p=0.123] and established risk factors for heart failure [odds ratio 1.47 (0.84-2.59); p=0.178]. Conclusions: Serum levels of 25(OH)D are not significantly associated with LV structure and function but a non-significant trend towards increased risk of diastolic dysfunction in persons with vitamin D deficiency warrants further studies. ©2010, Editrice Kurtis.