In this study we report the mutation analysis performed in Cuban PKU patients using DGGE and direct sequencing. Sixteen different mutations have been detected, which account for 91% of the total mutant alleles. Haplotype analysis and genealogical data support the European (mainly Spanish) origin of the mutations. Two mutations were found at unexpectedly high frequencies, E280K and R261Q, possibly due to consanguinity and genetic drift, among other factors. Hum Mutat 18:252, 2001.