Background: Left atrial (LA) function is an important determinant of left venricular (LV) filling. However, the effect of pulmonary hypertension (PH) on LA mechanical function in chronic obstructive lung disease (COLD) has not been studied, yet. Methods: 49 patients with COLD and 25 controls were included in this study. Patients were divided into two subgroups: patients without PH (group 1, n = 21) and with PH (group 2, n = 28). LA volumes were determined at mitral valve opening (Vmax), at onset of atrial systole (Vp) and at mitral valve closure (Vmin) according to biplane area-length method. The following LA parameters were calculated: passive emptying volume (PEV = Vmax - Vp), conduit volume [CV LV stroke volume - (Vmax - Vmin)], passive emptying fraction (PEF = PEV/Vmax), active emptying volume (AEV = Vp - Vmin), active emptying fraction (AEF = AEV/Vp), total emptying volume (TEV = Vmax - Vmin), percent contribution of PEN CV and AEV to LV stroke volume. Results: Vmax (p < 0.01), PEV (p < 0.001) and TEV (p < 0.05) were lower in group 2 than in the controls, and the differences between group I and control group were insignificant (p>0.05). Vp, Vmin, CV and AEV did not differ among three groups. Percent contribution to LV filling of the PEV was decreased in group 2 when compared to group I (p < 0.05) and the controls (p < 0.01). Percent contribution to LV filling of the AEV was increased in group 2 when compared to the controls (p < 0.05). There were inverse correlations between Pulmonary artery pressure and the following parameters: LV stroke volume (r = - 0.43, p < 0.01), mitral E/A (r = - 542 p < 0.001), Vmax (r = - 0.35, p < 0.05), PEV (r = - 40, p < 0.01) and PEF (r = - 0.43, p < 0.01). Conclusion: This study shows that the alterations of LA mechanical functions in patients with COLD are closely correlated to PH levels. Furthermore, these results underline the importance of maintaining a sinus rhythm in these patients. (C) 2003 Elsevier Ireland Ltd. All rights reserved.