Hereditary diffuse gastric cancer has an early onset and poor prognosis, therefore, individuals who carry a pathogenic (CDH1) mutation in the E-cadherin gene (CDH1) are offered endoscopic surveillance and advised to undergo prophylactic total gastrectomy (PTG) in their early to mid-twenties. Patients not ready or fit to undergo gastrectomy, or in whom the genetic testing result is unknown or ambiguous, are offered surveillance. Little is known about the factors that influence decisions to undergo or decline PTG, making it difficult to provide optimal support for those facing these decisions. Qualitative interviews were carried out with 35 high-risk individuals from the Familial Gastric Cancer Study in the UK. Twenty-seven had previously undergone PTG and eight had been identified as carrying a pathogenic CDH1 mutation but had declined surgery at the time of interview. The interviews explored the experience of decision-making and factors influencing risk-management decisions. The data suggest that decisions to proceed with PTG are influenced by a number of potentially competing factors: objective risk confirmation by genetic testing and/or receiving a positive biopsy; perceived familial cancer burden and associated risk perceptions; perceptions of post-surgical life; an increasing inability to tolerate endoscopic procedures; a concern that surveillance could miss a cancer developing and individual's life stage. These findings have implications for advising this patient group.