OBJECTIVES: To assess whether, compared with previous years, hospital care became safer in 2011/2012, expressing itself in a fall in preventable adverse event (AE) rates alongside patient safety initiatives. DESIGN: Retrospective patient record review at three points in time. SETTING: In three national AE studies, patient records of 2004, 2008 and 2011/2012 were reviewed in, respectively, 21 hospitals in 2004, 20 hospitals in 2008 and 20 hospitals in 2011/2012. In each hospital, 400, 200 and 200 patient records were sampled, respectively. PARTICIPANTS: In total, 15 997 patient admissions were included in the study, 7926 patient admissions from 2004, 4023 from 2008 and 4048 from 2011/2012. INTERVENTIONS: The main patient safety initiatives in hospital care at a national level between 2004 and 2012 have been small as well as large-scale multifaceted programmes. MAIN OUTCOME MEASURES: Rates of both AEs and preventable AEs. RESULTS: Uncorrected crude overall AE rates showed no change in 2011/2012 in comparison with 2008, whereas preventable AE rates showed a reduction of 45 per cent. After multilevel corrections, the decrease in preventable AE rate in 2011/2012 was still clearly visible with a decrease of 30 per cent in comparison to 2008 (p=0.10). In 2011/2012, fewer preventable AEs were found in older age groups, or related to the surgical process, in comparison with 2008. CONCLUSIONS: Our study shows some improvements in preventable AEs in the areas that were addressed during the comprehensive national safety programme. There are signs that such a programme has a positive impact on patient safety. [Abstract]