The levels of four brominated compounds in Lanice conchilega were measured: 2,4-dibromophenol, 2,6-dibromo-4-methylphenol, 2,4,6-tribromophenol, 3,5-dibromo-4-hydroxybenzaldehyde. The presence of all four of these secondary metabolites in the mu g/g range was species specific. Ten other terebellid species did not contain the compounds in significant concentrations. The levels were not dependent on animal size, sex or seasons. Bromophenols were not detected in plankton and only 2,4,6-tribromophenol was found in sea water (2 pg/g) near the sites of dense populations of the annelid. The compounds are generally not accumulated, which was tested by feeding pieces of L. conchilega to three marine invertebrate species.