BACKGROUND: Non-dippers were reported as showing different left atrial function, compared to dippers, but no study to date investigated the changes in the left atrial function according to the diurnal blood pressure pattern, using tissue Doppler and strain imaging. METHODS: Forty never treated hypertensive patients between 30 and 80 years of age were enrolled in this study. Patients were classified as non-dippers when, during night time, they had a blood pressure decrease of less than 10%. Strain of the left atrium was measured during late systole, and peak strain rates of the left atrium were measured during systole, early and late diastolic periods. RESULTS: The left atrial expansion index, left atrial active emptying volume and left atrial active emptying fraction were all significantly increased in non-dippers. They also had increased values of mean peak left atrial strain (dippers = 21.26 +/- 4.23% vs. non-dippers = 24.91 +/- 5.20%, p = 0.02), strain rate during reservoir (dippers = 1.29 +/- 0.23 s-1 vs. non-dippers =1.52 +/- 0.27 s-1, p = 0.01) and contractile period (dippers = -1.38 +/- 0.24 s-1 vs. non-dippers = -1.68 +/- 0.32 s-1, p < 0.01). CONCLUSION: Strain and strain rate acquired from color Doppler tissue imaging demonstrate exaggerated reservoir and booster pump function in never-treated, non-dipper hypertensive patients. These methods are simple and sensitive for the early detection of subtle changes in the left atrial function.