A comparative study of some tagging methods for the great scallop (Pecten maximus) is reported and intended to increase reliability and reduce costs associated with tagging. Tags were tested for ease of application, legibility, visibility and retention prior to a 17-month study of Pecten maximus in suspended (pearl net) culture. Of the six adhesives tested (standard epoxy resin, rapid epoxy resin, underwater epoxy resin, dental cement, cyanoacrylate fluid and cyanoacrylate gel), rapid epoxy resin and both cyanoacrylates were successful, bonding strongly and quickly to scallop shells. Of the three tag types used, Shellfish Tags (Hallprint) were favoured because they were simpler to apply, more visible, easier to read, and held more data than both Micromarkers (Brady) and engraved codes. In long-term trials 550 scallops were double tagged with Shellfish Tags using cyanoacrylate gel. Loss rates were 16% for tags on the umbo and 0·4% for tags positioned in grooves near to the shell margin. Loss rates did not increase over the 17-month period.