Alpha1-antitrypsin (alpha1-AT) deficiency is diagnosed as a two-stage procedure (concentration and phenotype). However the latter does not provide clues to the presence of null genes without family studies and obtaining blood from patients at a distance often proves difficult. The aim of the study was to assess the feasibility of genotyping alpha1-AT using buccal cells. Mouthwash specimens were sent by 84 patients (with a variety of phenotypes of alpha1-antitrypsin) through the post. Deoxyribonucleic acid (DNA) was isolated from buccal cells in each sample and subjected to polymerase chain reaction (PCR) using a genotyping kit to detect the S and Z alleles. Eighty-three of 84 samples received were suitable for amplification. The specific primers successfully identified the S and Z alleles in each case. However, five of the 35 samples obtained from patients thought to be Z allele homozygotes were found to be heterozygotes for another severe deficiency allele. These data confirm the feasibility of "at distance" testing for alpha1-antitrypsin deficiency alleles using buccal cells from mouthwash samples. The results raise the possibility that other deficiency alleles are more common than has previously been suspected.