Metallothioneins (MTs) are small, cysteine-rich proteins that can reflect the existence of heavy metal pollution. The coral prawn Metapenaeopsis crassissima is unique among crustaceans because females contain up to 100 times more Cd than the males. To investigate this phenomenon, 150 prawns from Western Australia (Exmouth, Carnarvon) were collected and 120 prawns were exposed to various levels of Zn, Cu, Cd and 106Cd in aquarium tests. Total element determinations (As, Ca, Cd, Cu, Co, Fe, Pb, Se, Zn) of 150 prawns were performed, each in duplicate, by using ICPMS following microwave-assisted acid digestion. The mean Cd content of the females was 80-fold higher compared to the males, thereby also a location dependent difference was revealed. Exmouth prawns contained significantly lower levels of Cd. Also a sex-related difference in the Se content of the prawns was determined, with the females exceeding the males by a factor of 2. The Cd-MT content was investigated in 90 individual prawns and the MTs were extracted. The obtained pellet was also analyzed to obtain a Cd mass balance, which showed a mean recovery of 9710 % and a mean extraction efficiency of 407 %. Speciation analysis was performed on a HPLC system (reversed-phase column, ammonium hydrogen carbonate buffer, gradient elution with methanol), the effluent was split post-column to the ICPMS (ca 22 %) and the rest went to an ESMS, therefore quantification and identification was obtained from a single chromatographic run. At least 7 Cd-MTs were detected and 4 MTs (5859, 5958, 6133, 6090 Da) could be identified. Male prawns accumulated Cd readily from solution, although probably not as efficiently as the females did. This result suggests that in their natural environment, water is unlikely to be a major contributor of Cd to the prawns.