Genetic polymorphism of apolipoprotein E (apoE) is linked with the risk of cardiovascular and Alzheimer's disease (AD). We determined apoE genotypes from mailed buccal cell swabs in 36 healthy individuals and 18 demented patients suffering from AD. DNA was released from the swabs by a rapid lysis technique. Polymerase chain reaction using 'hot start' and restriction enzyme digestion by HhaI was used for genotyping of apoE alleles, which were detected by polyacrylamide or MetaPhor agarose gel. ApoE genotypes determined from buccal cells or from stored leucocytes were identical to previously done phenotyping. An advantage of the present simplified buccal cell collection procedure is the possibility to collect DNA samples for apoE genotyping rapidly by mail from patients visiting their physician geographically distant from research laboratory. Moreover, venepuncture and storing of the samples in refrigerators are avoided and costs are reduced. This non-invasive and painless method is also applicable to other genetic screening tests in risk populations.