Twinkling artifact characterized by a rapidly fluctuating mixture of Doppler signals occurs behind a strongly reflecting granular interface such as urinary tract stones or gallstones. It may occurs in association with several clinical situations, and may sometimes be helpful for diagnosis while it may sometimes be a pitfall that must be recognized by the sonographer. After reviewing the technical nature of this artifact, several cases will be presented to illustrate the advantages and pitfalls related to this artifact.