Background Changes to the efficiency and integrity of swallowing mechanisms are inevitable in Parkinson's disease (PD). It remains unclear how many people with PD are at risk of dysphagia. Aims To establish the frequency of impaired swallowing on a bedside screening test in people with PD and the relationship of performance to indicators of disease progression. Methods 137 individuals with PD from a community and hospital based cohort were asked to drink 150ml of water as quickly as possible whilst in an 'off drug' state. Performance was timed live. Measures of swallow speed and volumes were derived. Outcomes were compared to published norms. Results Thirty-one (23%) could not complete the full 150ml. Swallowing rate (ml/sec) fell >-1SD below published norms for 115 (84%) and >-2SD for 44 (32%) subjects. There were moderate correlations between rate of swallow and disease severity (UPDRS, Hoehn and Yahr stage), depression and cognition, but not disease duration. Participants with a postural instability gait disorder (PIGD) phenotype performed significantly poorer. A best fit regression model (multiple R2 0.375) included the variables age, gender, depression, motor phenotype and UPDRS III score. There was poor correspondence between subjective reports of dysphagia and performance on the water swallow test. Conclusions Swallowing problems are frequent in PD. Older women and subjects with a PIGD phenotype are more at risk of dysphagia. Self-report of "no difficulty" is not a reliable indicator of swallowing status. Studies employing more objective assessment of aspiration (risk) to compare with water swallow test performance are advocated.