The Atlantic-Mediterranean area has recently been proposed as a new phylogeographical area on the basis of concordance of genetic differentiation patterns observed in several marine species. However, additional taxa need to be studied to establish the phylogeographical relationship between the Atlantic and Mediterranean. Eleven samples of the cuttlefish Sepia officinalis around the Iberian Peninsula, one from the Canary Islands, and another from Fiumicino (Italy) were screened for 33 allozyme loci. Genetic variability was low in all samples (He between 0.022 and 0. 076). Intersample genetic differentiation was high (FST=0.220), mainly because of genetic variation in the non-Iberian samples. One locus (PEPD*), diagnostic between the Italian sample and all others, suggests the possible existence of hitherto unrecognized species or subspecies of Sepia in the Mediterranean Sea. The 11 Iberian samples exhibited moderate genetic differentiation (FST=0.100), which could be explained on the basis of genetic differentiation between Atlantic and Mediterranean samples. Significant clines in allele frequencies were observed for five out of six polymorphic loci. These results support a model of secondary intergradation (i.e. secondary contact of populations that were previously differentiated in isolation) similar to that previously proposed for other marine species from the Atlantic-Mediterranean area.