Ultrasound is a promising diagnostic method when it comes to assessing the involvement of major salivary glands in patients with primary Sjögren's syndrome (pSS). A matter of debate is whether ultrasound of the major salivary glands (SGUS) can replace a salivary gland biopsy in the diagnosis or classification of pSS. The intra- and inter-observer reliability of SGUS was found to be good, especially when focusing on hypoechogenic areas and homogeneity, and comparable to the reliability of histopathologic characteristics of salivary gland biopsies of pSS patients. However, replacing salivary gland biopsy by SGUS led to substantial decrease of the accuracy of the 2016 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) classification criteria with clinical diagnosis as the gold standard. When SGUS was added as an additional item to the criteria, the accuracy of the criteria remained high, offering at the same time the clinicians a wider array of tools to assess patients. Combination of SGUS and anti-SSA antibodies was shown to be highly predictive of the classification of a patient suspected of pSS, making routine salivary gland biopsy debatable.