Only limited data are available from which normal ranges of mitral annular (MA) and tricuspid annular (TA) dimensions have been established. Normative data are important to assist the echocardiographer in defining the mechanism of atrioventricular valve regurgitation and to inform surgical planning. This study was conceived to establish normal MA and TA dimensions. Consecutive healthy subjects over the age of 60 were randomly recruited from the community as part of a screening project within South Birmingham. MA and TA dimensions in end-systole and end-diastole were evaluated in the parasternal and apical acoustic windows views using transthoracic echocardiography. Gender (males (M) and females (F))-specific dimensions were then assessed. A total of 554 subjects were screened and 74 with pathology considered to have an effect on annular dimensions were excluded from analysis. The mean age of the remaining 480 subjects was 70±7 years and the majority were female (56%). Dimensions were larger in men than in women and greater at end-diastole than end-systole (both P<0.05). Mean MA diameters at end-systole in the parasternal long axis view (cm) were 3.44 cm (M) and 3.11 cm (F) and at end-diastole 3.15 cm (M) and 2.83 cm (F) respectively. Mean TA diameters (cm) at end-systole in the apical 4 chamber view were 2.84 (M) and 2.80 (F) and at end-diastole 3.15 (M) and 3.01 (F) respectively. The reference ranges derived from this study differ from current published standards and should help to improve distinction of normal from pathological findings, in identifying aetiology and defining the mechanism of regurgitation.