This is the final version of the article. Available from Royal College of General Practitioners via the DOI in this record. ; BACKGROUND: Continuity of care may affect the diagnostic process in cancer but there is little research. AIM: To estimate associations between patient-doctor continuity and time to diagnosis and referral of three common cancers. DESIGN AND SETTING: Retrospective cohort study in general practices in England. METHOD: This study used data from the General Practice Research Database for patients aged ≥40 years with a diagnosis of breast, colorectal, or lung cancer. Relevant cancer symptoms or signs were identified up to 12 months before diagnosis. Patient-doctor continuity (fraction-of-care index adjusted for number of consultations) was calculated up to 24 months before diagnosis. Time ratios (TRs) were estimated using accelerated failure time regression models. RESULTS: Patient-doctor continuity in the 24 months before diagnosis was associated with a slightly later diagnosis of colorectal (time ratio [TR] 1.01, 95% confidence interval [CI] =1.01 to 1.02) but not breast (TR = 1.00, 0.99 to 1.01) or lung cancer (TR = 1.00, 0.99 to 1.00). Secondary analyses suggested that for colorectal and lung cancer, continuity of doctor before the index consultation was associated with a later diagnosis but continuity after the index consultation was associated with an earlier diagnosis, with no such effects for breast cancer. For all three cancers, most of the delay to diagnosis occurred after referral. CONCLUSION: Any effect for patient-doctor continuity appears to be small. Future studies should compare investigations, referrals, and diagnoses in patients with and without cancer who present with possible cancer symptoms or signs; and focus on 'difficult to diagnose' types of cancer. ; This work was funded by Cancer Research UK (C41384/A13266).