OBJECTIVE: To develop a uniform classification and standardized reporting system of ultrasound findings of adenomyosis using the Morphological Uterus Sonographic Assessment (MUSA) criteria. METHOD: The opinion presented in this manuscript was built based on a thorough discussion among all authors, including a Delphi procedure. Selected images and videos of typical cases of the different morphological variations of adenomyosis were used in the debates. RESULTS: A classification and reporting system of different types of adenomyosis based on ultrasound was agreed upon including (1) identification of adenomyosis based on MUSA criteria, (2) disease location (anterior, posterior, left lateral, right lateral, fundal), (3) classification of the lesions as focal or diffuse, (4) presence or absence of intralesional cysts, (5) myometrial layer involvement (junctional zone, myometrium, serosal involvement), (6) disease extent (< 25%, 25-50%, > 50% of uterine volume affected by adenomyosis) and (7) lesion size. CONCLUSIONS: We proposes a uniform classification and reporting system of different types of adenomyosis based on ultrasound. The clinical relevance of this approach needs to be evaluated in further studies. This article is protected by copyright. All rights reserved.