Background: Preoperative preparation for elective surgery is time and resource-consuming processes for patients, their families as well as hospital personnel. Cancellations do have emotional and economic impact. Knowing the rater and causes is useful for improving hospital service. Objectives: To determine the rate and rationales for cancellation of elective surgery Study design: Prospective Descriptive Study Setting : Srinagarind Hospital, Faculty of Medicine, Khon Kaen University Subjects: Elective surgical patients whom were schedule from September 1, 1999 to January 31, 2000. Main outcome measures: The total number of patients scheduled for elective surgery as well as the number of cancellation cases was daily recorded. The reasons for cancellation were explored by interviewing surgeons, anesthesiologists and scrub nurses who were responsible within the same day of cancellation. The reasons were divided into 3 groups according to the main factors; group 1: doctors factor, group 2: patients factor and group 3: hospital services factor. Results: There were 4, 121 patients scheduled for elective surgery during the study period. Four hundred and nine cases were cancelled which resulted in 9.9% (95% CI: 9.0%-10.9%) cancellation rate. Most of the cases were from department of surgery. The main reasons for cancellation were from doctor 57.4%, from patients 40.1% and from hospital service 2.4%. Overscheduled cases for surgery in a limited time was the most common reason found in the doctor group while, in the patient group, the reason were associated medical problems which were unsuitable for anesthesia and surgery. Conclusion: The study shows that Srinagarind hospital has 9.9% cancellation rate. In order to decrease emotional and economic impact for patients and their families as well as to maximize resource utilization, appropriate strategies should be developed to prevent unnecessary cancellation.