DPI 201-106 is a novel compound unrelated to other cardioactive agents and has been shown to have an inotropic effect in animal preparations. The drug was given by intravenous infusion (20 mg over 10 min) to 10 patients with moderate cardiac failure and the haemodynamic effects measured at intervals up to 1 h following infusion. Maximal effects were seen immediately following the infusion of DPI 201-106. Cardiac index showed an increase from baseline 2.72 (0.16) 1 min-1 m-2 to 3.18 (0.21) 1 min-1 m-2 at the end of infusion (P less than 0.001). Subsequent values were not significantly raised. Pulmonary capillary wedge pressure and pulmonary artery pressure fell from 27.6 (3.2) and 36.9 (4.4) to 15.3 (3.6) and 24.2 (4.9) mmHg, respectively (P less than 0.001 in both cases). A statistically significant effect on cardiac index was not seen at 1 h. However, pulmonary pressures remained reduced at this point. Radionuclide ejection fraction showed a significant increase from 15.4 (1.5) to 21.9 (2.2)% (P less than 0.005) at the end of infusion, and maintained a significant increase at 1 h. Having demonstrated beneficial, acute haemodynamic effects in this study, further work should be undertaken with DPI 201-106 to investigate the effect of chronic treatment in patients with cardiac failure.