Background Preventable medical errors continue to be a major cause of death in the USA and throughout the world. Many patients have written about their experiences on websites and in published books.

Methods As patients and family members who have experienced medical harm, we have created a nationwide voluntary survey in order to more broadly and systematically capture the perspective of patients and patient families experiencing adverse medical events and have used quantitative and qualitative analysis to summarise the responses of 696 patients and their families.

Results Harm was most commonly associated with diagnostic and therapeutic errors, followed by surgical or procedural complications, hospital-associated infections and medication errors, and our quantitative results match those of previous provider-initiated patient surveys. Qualitative analysis of 450 narratives revealed a lack of perceived provider and system accountability, deficient and disrespectful communication and a failure of providers to listen as major themes. The consequences of adverse events included death, post-traumatic stress, financial hardship and permanent disability. These conditions and consequences led to a loss of patients’ trust in both the health system and providers. Patients and family members offered suggestions for preventing future adverse events and emphasised the importance of shared decision-making.

Conclusions This large voluntary survey of medical harm highlights the potential efficacy of patient-initiated surveys for providing meaningful feedback and for guiding improvements in patient care.