Observations on the metal used as pins for Petersen-type tags onParophrys vetulusshowed manufactured nickel pins to be most subject to corrosion or wear, with pins of silver wire, nickel and stainless steel wire successively less liable. Tagging wounds were worst with nickel pins and least with stainless steel wire. A correction factor of approximately 1.7 for each year the tag is out is necessary to bring results with nickel pins on a par with those of stainless steel wire.