The objective of this chapter is to relate the image findings of transvaginal ultrasound (TVS) to structural changes of adenomyosis; in order to clarify the present clinical diagnostic approach in the diagnosis of adenomyosis, the performance of TVS is evaluated in comparison to other diagnostic modalities. A Medline search of papers in English on the use of TVS and needle biopsy for the diagnosis of adenomyosis was carried out. It was found that TVS is highly observer-dependent, but in the hands of experienced investigators it has an adequate diagnostic accuracy in clinically suspected cases. The diagnostic accuracy of TVS is at an intermediate level but is in line with that of magnetic resonance imaging (MRI) in unselected patients without myomas undergoing surgery. TVS is a sufficiently accurate tool for diagnosis of adenomyosis in clinically suspected cases, but not in unselected premenopausal women with myomas. Resectoscopic hysteroscopic biopsy has not been sufficiently evaluated but could be a useful diagnostic tool, whereas needle biopsy is not. In conclusion, in clinically suspected adenomyosis cases TVS should be favoured as the primary diagnostic tool. Substantial experience and specific training is required for TVS to be a useful diagnostic tool in adenomyosis. MRI may be considered when TVS is inconclusive. Clinicians should above all be observant of image findings of adenomyosis in patients with no wish to preserve fertility.