Radio tagged common carp Cyprinus carpio in a Namibian reservoir, where this species has been introduced, experienced 100% mortality or tag loss ( n = 13) with surgically implanted transmitters and 100% survival ( n = 5) with externally attached transmitters at water temperatures of 24–25° C. It seems that the negative effects of the tagging were greater for surgical implantation than for external attachment. The body shape of common carp make them well suited for external tagging, and this tagging method is recommended for common carp studies at high water temperatures or under other stressful conditions. Keywords: common carp, Cyprinus carpio, radio transmitters, tag effects, telemetry.