STUDY OBJECTIVES: To study the location, distribution, and intensity of pain in a sample of adult cardiac surgery patients during their postoperative hospital stay. DESIGN: In a prospective study, pain location, distribution (number of pain areas per patient), and intensity (0 to 10 numerical rating scale) were documented on the first, second, third, and seventh postoperative day (POD). Patient characteristics (age, sex, size, and body mass index) were analyzed for their impact on pain intensity. SETTING: A university hospital. PATIENTS: Two hundred consecutive adult patients who underwent median sternotomy for open heart surgery. There were 121 male and 79 female patients, with a mean (+/- SD) age of 60.9 +/- 19.2 years. Measurement and results: The maximal pain intensity was significantly higher on POD 1 and 2 (3.7 +/- 2 and 3.9 +/- 1.9, respectively) and lower on POD 3 and 7 (3.2 +/- 1.5 and 2.6 +/- 1.8, respectively). The pain distribution did not vary significantly throughout the hospital stay, but the location did, with more shoulder pain on POD 7. Only age was found to have an impact on pain intensity, with patients < 60 years having a higher pain intensity than older patients on POD 2 (4.3 +/- 2.2 vs 3.6 +/- 2.4; p = 0.02). CONCLUSIONS: In this patient population, the pain intensity diminished from POD 3 onward, although its distribution did not vary significantly during the first postoperative week. Moreover, pain location changed with time, with more osteoarticular type pain at the end of the first postoperative week. Among the patients' characteristics, only younger age had an impact on pain intensity, with a higher value on POD 2.