Previous morphological studies of Illex coindetii from the Mediterranean have shown both juvenile and mature individuals all year round suggesting an homogeneous population pattern, however, seasonal spawning variation seems to exist varying with geographical area. Present work analysed 240 individuals from the northern Tyrrhenian and Atlantic Iberian waters at the four year-round seasons using 33 presumptive enzyme-coding loci to compare geographical and temporal variances. Genetic variability was low (Ho=0·02–0·04). Moderate variation at some loci was found due to both temporal and geographical factors (12% of total genetic variance) and to temporal variance (FST=0·004–0·015). Unweighted pair-group method using arithmetric averages (UPGMA) and Multidimensional scaling–minimum spanning tree (MDS–MST) analyses after Cavalli-Sforza & Edwards (1967) chord genetic distances showed the summer Italian and the spring Atlantic samples as the most divergent among the whole.