Traceability during slaughter was studied in 1,581 pigs identified by different devices. Treatments were visual ear tags (n = 1,300), electronic ear tags of different technologies (half-duplex, n = 636; full-duplex, n = 632), and intraperitoneally injected transponders of different technologies (half-duplex 32 mm, n = 645; full-duplex 34 mm, n = 642). Piglets were individually identified at weaning and intensively fed until 100 kg of BW. Pigs were slaughtered in 2 commercial slaughterhouses (including scalding, flaming, and peeling) at different throughputs (450 and 550 pigs/h). Readability during slaughtering was checked visually and using standardized handheld transceivers. No effect of slaughterhouse was detected (P > 0.05). Ear tag losses in the slaughtering line were similar for visual (3.7%) and half-duplex (3.5%) but were increased for full-duplex (11.5%; P < 0.05). Moreover, electronic failures during slaughtering did not differ (P > 0.05) between ear tags (half-duplex, 1.1%; full-duplex, 0.6%). Intraperitoneally injected transponders were not affected by slaughtering (retention 100%, no failures), and 89.0% of the transponders were manually recov ered from the abdominal viscera in the offal trays. The remaining transponders (11.0%) were lost on the floor, but none were found in the carcasses. No differences (P > 0.05) in recovery were observed between intraperitoneal transponders. Considering on-farm and slaughterhouse data, total traceability from farm to carcass release was greater (P < 0.05) for intraperitoneally injected transponders (98.2%) than for ear tags. Between ear tags, the greatest traceability was obtained with visual tags (95.7%), which differed (P < 0.05) from electronic tags (half-duplex, 91.4%; full-duplex, 84.5%; P < 0.05). Intraperitoneally injected transponders were an efficient and reliable identification system for tracing pigs from farm to the end of the slaughter line, allowing the transfer of pig identification to the carcass. Adherence of intraperitoneally injected transponders to the viscera should be improved to reduce risks of loss in the meat chain. A dual system based on intraperitoneally injected transponders and plastic ear tags would allow a redundant and automatic reading system that is efficient and reliable for data management and traceability in the swine industry.