Pindolol has the most intrinsic sympathomimetic activity (ISA).

Beta-blockers with ISA only partially antagonize while actually causing a small degree of activation of the beta receptors. So they will have some beta-blocking effects, but not to the degree of beta-blockers without ISA. These are commonly used in younger patients or in athletes where heart rates need to elevate (allowing overall increased cardiopulmonary effort) in order to compete in sports. Examples include pindolol and acebutolol.