The review describes the historical development and nomenclature of Sjögren's syndrome--primary and secondary. The strengths and weaknesses as well as similarities and dissimilarities for establishing the diagnosis of keratoconjunctivitis sicca and xerostomia used among the five most commonly classification criteria sets are focused upon in text and table. Validation of the different sets of criteria are performed. Primary and secondary disease activity markers and outcome measures as well as future research plans for improving diagnosis are dealt with.