The presence of a positive clinical history and skin test (ST) results for 17 fish species (anchovy, bass, carp, dogfish, eel, gilthead, mackerel, mullet, perch, red mullet, salmon, sardine, sole, tench, toothed gilthead, trout, and tuna) were investigated in 20 children with cod-positive clinical history, ST, and RAST, and in 40 children positive to one or more foods different from cod (cow's milk, chicken egg white, peanut, and tomato). In cod-positive children, positive clinical history (60%) and ST (85%) to fish species were more frequent than in cod-negative children (7.5% and 10% respectively). In cod-positive children, a high frequency of positive STs to eel (85%) and to bass, dentex, sole, and tuna (55%) was observed. Positivity to dogfish (10%) was the least frequent. RAST-inhibition experiments suggested the presence of cross-reacting antigen(s) in cod, bass, dentex, eel, sole, and tuna. Results of this study demonstrate that cod allergy might be, on the whole, a reliable index of fish allergy, but cod-positive children may perhaps tolerate some other species, which will have to be tested for possible inclusion in their diet.