The purpose of the present study was to investigate the differences in salivary flow rates and dry mouth-related subjective symptoms and behaviours in patients with xerostomia according to its aetiology. One hundred and forty patients (24 men and 116 women, mean age, 58·1 ± 13·3 years) with a chief complaint of xerostomia were included. The patients were divided into five groups; Sjögren's syndrome (n = 34), post-radiation therapy in the head and neck region (n = 16), antipsychotic medications (n = 30), systemic diseases or medications affecting salivary flow (n = 35), and unknown aetiology (n = 25). The patients were asked a standardized series of questions concerning dry mouth, and their whole salivary flow rates were measured. Patients w...