The Andersen-Tawil syndrome (ATS) is an autosomal dominant or sporadic disorder characterised by periodic paralysis, cardiac arrhythmias and dysmorphic features. Mutations in KCNJ2, which encodes the inward rectifier K+ channel Kir2.1 can be found in approximately 70% of ATS cases. The genetic mechanism in the remaining 30% of patients is still unknown. We present ECG of a 19-year-old man with the Andersen-Tawil syndrome. The standard ECG revealed prominent U wave with the ATS TU pattern.