AIM: To assess the role of lactase non-persistence/persistence in school-aged children and their milk-related symptoms. METHODS: The genotypes for the C/T-13910 variant associated with lactase non-persistence/ persistence were determined using PCR-minisequencing in a group of 172 children with a mean age of 8.6 years (SE = 0.02, 93 boys) participating in a follow-up study for cow’s milk allergy. The parents were asked to assess their children’s milk consumption and abdominal symptoms. RESULTS: The presence of allergy to cow’s milk was not associated with the C/C-13910 genotype related with a decline of lactase enzyme activity during childhood (lactase non-persistence). The frequency of the C/C-13910 genotype (16%) was similar to published figures for the prevalence of adult-type hypolactasia in Finland. The majority of the children (90%) in this series consumed milk but 26% of their families suspected that their children had milk-related symptoms. Forty-eight percent of the children with the C/C-13910 genotype did not drink milk at all or consumed a low lactose containing diet prior to the genotyping (P< 0.004 when compared to the other genotypes). CONCLUSION: Analysis of the C/T-13910 polymorphism is an easy and reliable method for excluding adult-type hypolactasia in children with milk-related symptoms. Genotyping for this variant can be used to advise diets for children with a previous history of cow’s milk allergy. METHODS: The genotypes for the C / T-13910 variant associated with lactase non-persistence / persistence were determined using PCR- The parents were asked to assess their children’s milk consumption and abdominal symptoms. RESULTS: Minutequencing in a group of 172 children with a mean age of 8.6 years (SE = 0.02, 93 boys) participated in a follow-up study for cow’s milk allergy. The presence of allergy to cow’s milk was not associated with the C / C-13910 genotype related with a decline of lactase enzyme activity during childhood (lactase non-persistence). The frequency of the C / C-13910 genotype (16%) was similar to published figures for the prevalence of adult-type hypolactasia in Finland. The majority of the children (90%) in this series consumed milk but 26% of their families suspected that their children had milk-related symptoms. Forty-eight percent of the children wi th the C / C-13910 genotype did not drink milk at all or consumed a low lactose containing diet prior to the genotyping (P <0.004 when compared to the other genotypes). CONCLUSION: Analysis of the C / T-13910 polymorphism is an easy and reliable method for excluding adult-type hypolactasia in children with milk-related symptoms. Genotyping for this variant can be used to advise diets for children with a previous history of cow’s milk allergy.