To ascertain the potential for exploiting marine areas for mariculture, data on the cultivation of molluscs and fish in the open sea of the southern Tyrrhenian were collected from May 1994 to June 1995. The aims of this integrated study were to test simple breeding methods for molluscs and fish, to apply these to the practices employed by local fishermen and to experiment with the use of a cage system requiring a low level of investment. Crassostrea gigas (Thunberg) and Mytilus galloprovincialis (Lamarck) were cultivated on submerged long lines around cages used for cultivating Seriola dumerili (Risso) and Diplodus puntazzo (Cetti). S. dumerili specimens were placed in two cages and fed with either fish scraps or pellets, while in a third cage, D: puntazzo were fed with pellets only. After a period of 12 months, the following results were obtained: the oysters measured 47.50 ± 12.30 mm and weighed 0.13 ± 0.09 g; the mussels placed in culture as juveniles reached a length of ≃40 mm, while the mussels placed in culture as subadults reached the commercial size of about 60 mm. The mean length and weight measurements of the two fish species were as follows: Diplodus 228 ± 14.4 mm and 228 ± 40.48 g; Seriola (lot A) 438.1 ± 25.28 mm and 1149 ± 172.2 g; Seriola (lot B) 347 ± 25.6 mm and 576 ± 139 g.