OBJECTIVE To investigate the aetiological factors and the prevalence of salivary gland hypofunction (SGH) in patients complaining of xerostomia. METHODS Prospective, clinical study. METHODS Xerostomia clinic in the Department of Oral Medicine at Liverpool University Dental Hospital. METHODS 100 consecutive patients, aged 60 years or older, referred for investigation of xerostomia. METHODS Patients were asked specific questions concerning their complaint of oral dryness and associated orofacial symptoms. A detailed medical history was recorded and patients underwent a systematic examination of the head, neck and oral structures. All patients underwent haematological, biochemical, immunological investigations, urinalysis and sialometry. Further investigations and referrals to other specialists were undertaken when appropriate. METHODS The causes of xerostomia were established on the basis of clinical and laboratory findings and SGH was defined as an unstimulated whole salivary flow rate of < 0.2ml/min, RESULTS The causes of xerostomia were identified as: Sjögren's Syndrome (40), iatrogenic (22), psychogenic (14), idiopathic (19), diabetes (1), candidosis (3) and alcohol (1). Sixty five percent of the patients studied had SGH. CONCLUSIONS This study has shown that 65% of patients whose presenting complaint was xerostomia had objective evidence of SGH. Several aetiological factors were identified, the most common of which was Sjögren's Syndrome. The possibility of associated systemic diseases should be considered when establishing the aetiology of SGH.