The glycoprotein 130 (gp130) signalling pathway is important in the development of heart failure. Cardiotrophin-1 (CT-1), a cytokine acting via the gp130 pathway, is involved in the process of ventricular remodelling following acute myocardial infarction (AMI) in animals. The aims of the present study were to examine the profile of plasma CT-1 following AMI in humans, and its relationship with echocardiographic parameters of left ventricular (LV) systolic function. Serial measurements of plasma CT-1 levels were made in 60 patients at 14-48h, 49-72h, 73-120h and 121-192h following AMI and at a later clinic visit. LV function was assessed using a LV wall motion index (WMI) score on admission (WMI-1) and at the clinic visit (WMI-2). Compared with values in control subjects (29.5±3.6fmol/ml), the plasma CT-1 concentration was elevated in AMI patients at 14-48h (108.1±15.1fmol/ml), 49-72h (105.2±19.7fmol/ml), 73-120h (91.2±14.9fmol/ml) and 121-192h (118.8±22.6fmol/ml), and at the clinic visit (174.9±30.9 fmol/ml) ( P < 0.0001). Levels were higher following anterior compared with inferior AMI. For patients with anterior AMI, CT-1 levels were higher at the clinic visit than at earlier times. WMI-1 correlated with CT-1 at all times prior to hospital discharge ( P < 0.05). On best subsets analysis, the strongest correlate with WMI-1 was CT-1 level at 49-72h ( R 2 = 20%, P < 0.05). In conclusion, plasma levels of CT-1 are elevated soon after AMI in humans and rise further in the subsequent weeks in patients after anterior infarction. CT-1 measured soon after AMI is indicative of LV dysfunction, and this cytokine may have a role in the development of ventricular remodelling and heart failure after AMI.