The aim of this study was to investigate transmitter attachment and longevity on Nile crocodiles (Crocodylus niloticus) in the Flag Boshielo Dam, Mpumalanga, South Africa. From August 2002, 15 adult Nile crocodiles were captured over a 19-month period in the Flag Boshielo Dam. Conventional VHF transmitters were fitted to the tails of eight male and five female Nile crocodiles, while a GPS / GSM transmitter was fitted dorsally to the neck of one male and one female Nile crocodile. There was no significant difference in the total lengths of male and female Nile crocodiles captured for transmitter fitment. Overall, 40% of the transmitters failed, while an equal number was broken off. Neither sex, nor total length of the Nile crocodiles predicted longevity of transmitters from time of fitment to time of failure or destruction and loss. In future, the tails of crocodiles should be avoided when attaching transmitters, as conspecifics seem to target this area during agonistic behaviour. Moreover, it is essential that transmitters and their attachment configurations be tested on the target species before a study commences. Lastly, we urge researchers to routinely provide information on the performance of transmitters and their fitment configurations.