We have investigated a series of FAP patients in the Northwest of England in order to identify and characterise the specific APC mutations. Using SSCP, we found 27 mutations in a total of 50 families investigated. The mutations were predominantly frameshift or nonsense mutations and there were two splice site changes. We have described two patients with severe Gardner's phenotype from different ethnic backgrounds who share the same mutation at codon 1537. Although the frequency of the most common mutation appears low, it is not dissimilar to that reported by other groups.