Background: A complete, correct and timely discharge letter can communicate important information from the hospital to the general practitioner. The adequacy of the letter may vary with the patient and admission characteristics of the patient. Insight in the association between these characteristics and the presence and quality of the discharge letter will give rise to improvement activities for a better continuity of care after discharge. The objective was to determine the presence, correctness and timeliness of admission information in discharge letters and to determine the association between patient and admission characteristics, including unplanned readmissions and the quality of the discharge letter. Methods: A post-hoc analysis of a two-staged retrospective patient record review study was performed in 4048 patient records in a random sample of 20 hospitals. Results: Nearly ten percent of the discharge letters are lacking in patient records in Dutch hospitals. In 59.1% of the discharge letters, one or more relevant components are missing. Important laboratory results, relevant information about consultations, answers to the questions of the referrer, changes in medication and follow up are often lacking. Discharge letters are more likely to be missing in elective patient admissions to a hospital, with a shorter length of stay, less comorbidity, and in readmissions. There was a significant variation in missing discharge letters between hospitals and between hospital departments. Conclusions: The quality of discharge letters varies with patient and admission characteristics.