The Carvedilol Acute Myocardial Infarction Study (CAMIS) investigates cardiac remodeling in patients (n = 250) randomized to carvedilol vs atenolol and treated for 12 months after acute myocardial infarction. In a sub-study, we compared sympathetic, hemorrheological and vascular effects in small but particularly well-matched groups of participants who had been on reasonably equipotent but unchanged doses of carvedilol (n = 10) or atenolol (n = 10) for at least 4 weeks. Blood pressures (p < 0.05), plasma adrenaline (p = 0.034), plasma vasopressin (p = 0.022) and whole blood viscosity at shear rate 0.5 cp (p = 0.050), 1.1 cp (p = 0.023), 5.8 cp (p = 0.049) and 201 cp (p = 0.060) taken in the laboratory at baseline before 2 h of using the hyperinsulinemic, isoglycemic glucose clamp were lower on carvedilol. Plasma noradrenaline was lower on carvedilol at baseline and throughout the clamp (p < 0.0005). Forearm vascular resistance as measured by plethysmography during the clamp tended to be lower on carvedilol (p = 0.074). No significant difference was found between the groups in glucose disposal rate measured by clamp, maximal forearm blood flow and minimal forearm vascular resistance after 10 min of ischemia, or in ambulatory blood pressure and heart rate taken a few days later. Thus, potential benefits of carvedilol vs atenolol were seen in these post-infarction patients in a laboratory setting. These findings suggest that the inhibitory effects on the sympathetic nervous system and related blood viscosity are stronger with carvedilol than with atenolol.