Potassium channels at the cardiomyocyte surface must eventually be internalized and degraded, and changes in cardiac potassium channel expression are known to occur during myocardial disease. It is not known which trafficking pathways are involved in the control of cardiac potassium channel surface expression nor is it clear whether all cardiac potassium channels follow a common pathway or many pathways. Here we survey the role of retrograde microtubule-dependent transport in modulating the surface expression of several cardiac potassium channels in ventricular myocytes and heterologous cells. The disruption of microtubule transport in rat ventricular myocytes with nocodazole resulted in significant changes in potassium currents. A-type currents were enhanced 1.6-fold at +90 mV, rising from control densities of 20.9±2.8 pA/pF to 34.0±5.4 pA/pF in the nocodazole-treated cells, whereas inward rectifier currents were reduced by a third, perhaps due to a higher nocodazole-sensitivity of Kir channel forward trafficking. These changes in potassium currents were associated with a significant decrease in action potential duration. When expressed in heterologous HEK293 cells, surface expression of Kv4.2, known to substantially underlie A-type currents in rat myocytes, was increased by nocodazole, by the dynein inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride (EHNA) and by p50 overexpression, which specifically interferes with dynein motor function. Peak current density was 360±61.0 pA/pF in control cells and 658±94.5 pA/pF in cells overexpressing p50. The expression levels of Kv2.1, Kv3.1, hERG and Kir2.1 were similarly increased by p50 overexpression in this system. Thus, the regulation of potassium channel expression involves a common dynein-dependent process operating similarly on the various channels.