Although high PhD attrition rates are a matter of international concern, the factors that lead doctoral researchers to leave their programmes are not well understood. The present study addresses that issue by exploring factors that prompted thoughts of discontinuing among 1017 PhD researchers (PhDRs) at a public, research-intensive Australian university. We analyse the prevalence, strength and clustering of the most frequently identified factors, including mental health difficulties, financial pressures, and problems with supervision. The investigated factors were all strongly associated with thoughts of discontinuing; mental health difficulties were among the strongest factors, and financial stress was the most prevalent. An exploratory cluster analysis revealed that the risk factors co-present in distinctive ways such that six discrete groups of PhDRs are identifiable with varying risk profiles and socio-demographic characteristics. We discuss the research, policy and practice implications of these findings.