Cyprids of the barnacleChthamalus montaguiSouthward were reared in the laboratory. Their preference for settlement on panels treated with con‐ or allospecific water soluble protein extracts was measured. Proteins derived fromC. montaguiadults promoted twice as much settlement as those from eitherB. balanoidesorE. modeslusadults. Settlement on control panels treated with phosphate buffer was very poor in comparison to any protein treatment. The behaviour of chthamalid larvae at settlement parallels that shown by balanid larvae.