Twenty‐seven deep‐water fish species from a number of locations around New Zealand were sampled between 1976 and 1980 to determine their flesh mercury levels. Twenty‐four species (1300 specimens) had mean mercury levels below 0.5 mg.kg‐1, the maximum permitted by the New Zealand Food and Drug Regulations (1973). The overall range was 0.02–2.40 mg. kg‐1. Mercury levels and fish length were positively correlated in 13 species. Locality effects were also detected; in ling (Genypterus blacodes), mercury levels in individuals from all but 2 of the 5 areas investigated were significantly different. Water temperature was considered to be an important factor because fast‐growing ling in warm waters generally had more mercury in their flesh than those from cooler regions.