Left ventricular (LV) diastolic dysfunction identifies patients at risk of developing heart failure and may be common in patients with hypertension. The prevalence of LV diastolic dysfunction in patients with newly diagnosed hypertension was compared using criteria provided by the Canadian Consensus, European Study Group, and American Medical Association guidelines. One hundred twenty patients with newly diagnosed untreated hypertension (mean age 46.9 +/- 2.1 years; 62 men, 58 women) with increased blood pressure (clinic >140/90 mm Hg, daytime ambulatory >135/85 mm Hg) underwent comprehensive 2-dimensional echocardiography. Transmitral inflow velocities were measured using pulse-wave Doppler with and without Valsalva's maneuver, and a comprehensive assessment of tissue Doppler velocities was performed. The prevalence of LV diastolic dysfunction varied according to criteria used. There was a high prevalence of LV diastolic dysfunction (59%; n = 71) using Canadian Consensus guidelines; 27% of patients (n = 32) had a pseudonormal pattern unmasked using Valsalva's maneuver and 32% (n = 39) had impaired relaxation at rest. Significantly fewer patients (10%; n = 12) had this diagnosis using European or American Medical Association guidelines (23%; n = 27). Using tissue Doppler imaging (early-late diastolic velocity ratio <1), the prevalence of LV diastolic dysfunction was 59% (n = 71), identical to findings using the Canadian Consensus guidelines. In conclusion, current national consensus guidelines defining LV diastolic dysfunction varied widely and underdiagnosed LV diastolic dysfunction in patients with newly diagnosed hypertension. Tissue Doppler imaging assessment is a rapidly and widely available tool that is as sensitive as the most stringent national guidelines and should be systematically incorporated into a more comprehensive assessment of LV diastolic dysfunction in this population.