Apolipoprotein E (apoE) gene polymorphism was analyzed by polymerase chain reaction in one Moroccan and six Spanish populations, a total of 660 individuals. No significant differences were observed between samples, and the mean relative frequencies (with 95% confidence intervals) found were 0.104 (0.069-0.139) for the epsilon4 allele, 0.855 (0.813-0.897) for epsilon3 and 0.041 (0.015-0.067) for epsilon2. Frequencies of the epsilon4 allele were low in comparison to Northern European populations, but similar to those reported for other South-European populations. The presence of a rare mutation, E2 Christchurch, in one Basque individual was confirmed by sequence analysis.