The lactose-loading test and other functional tests that have been the most widely used clinically in the diagnosis of adult hypolactasia up to now are labour intensive and costly, and suffer from low sensitivity as well as low specificity. In addition, lactose-loading tests may be painful to the patient. Here, a new genotyping method for the diagnosis of adult hypolactasia is described. The method utilizes Pyrosequencing technology, which gives the DNA sequence around the recently identified C/T polymorphic site in the MCM6 gene. Among the advantages compared to the other genotyping methods published are less staff hands-on time than for example RFLP analyses, and the avoidance of radioactivity, as in the originally described isotope-minisequencing. Most importantly, Pyrosequencing, which is a direct DNA sequencing technique, gives unambiguous genotyping results as well as some redundant sequence information beyond the SNP position, which serves as a valuable internal control, obtained for each sample.