In the present study, we investigated the immunohistochemical localization of two-pore K(+)-channels TASK-1, TASK-2, TASK-3 and TRAAK in the rat carotid body. Type I cells were positive for TASK-1, TASK-2, TASK-3 and TRAAK. Intrinsic nerve cell bodies were also strongly positive for TASK-1, TASK-2 and TRAAK, but negative for TASK-3. In addition, some type II cells, Schwann cells in the nerve bundles and fibroblast between type I cell clusters were also immunostained for TASK-1. Smooth muscle cells of the carotid body artery were intensely positive for TASK-3. Our results indicate that TASK-1 immunoreactivity was ubiquitously distributed in many cell types and immunoreactivities for TASK-2, TASK-3 and TRAAK were cell type specific distribution patterns in the rat carotid body.