OBJECTIVE: To quantify the different stages of diagnostic delay of pulmonary embolism (PE) in patients and to identify other clinical factors associated with this delay. DESIGN: Case series. METHOD: Medical records were reviewed for all patients diagnosed with PE in the period 1 January 2008 and 31 December 2009 in Isala Hospital in Zwolle (the Netherlands), and data was collated for: the dates of symptom onset, presentation to a GP, referral to secondary care, and diagnosis respectively. The relationship between diagnostic delay and other clinical parameters such as gender, age, risk factors, symptoms and co-morbidities was tested using multivariate logistic regression analysis. RESULTS: For the 261 patients included in the analysis, the average total delay was 8.6 days. Patient delay (4.2 days average) and delay in primary care (3.9 days) were the major contributors to this delay. Chest pain and symptoms of deep venous thrombosis were associated with an early diagnosis. Patient delay was shorter in patients with chest pain and longer in patients with dyspnoea. In primary care, chest pain and rales were associated with an early referral, whereas the presence of co-morbidity led to a delayed referral. Delay in secondary care was shorter when the patient presented with dyspnoea. CONCLUSION: The diagnostic delay of PE is substantial, especially patient delay and delays originating in primary care. Further research is needed to identify clinical factors that raise suspicion of PE in primary care, to aid the development of improved diagnostic models