Some factors influencing the metamorphosis and settlement of the larvae of the barnacle Balanus amphitrite amphitrite Darwin, in the laboratory were studied. The diatom Nitzschia closterium when used as food facilitated larval metamorphosis while the green alga Dunaliella primolecta was found unsuitable even in the early stages of metamorphosis. Larvae metamorphosed under normal daylight illumination, whereas they reached only up to V naupliar stage under total darkness. The addition of penicillin to the rearing vessels had no significant improvement in the total yield. Sterilised sea water medium, interestingly enough, did not support larval metamorphosis