Background: The shelf life policies for central supply department (CSD) sterilized items and other devices should be determined by the healthcare facility's infection control program. We investigated effect of the sterility integrity of the CSD sterilized packs by wrapping-materials, storage period and environment to modify and extend current shelf-life. Methods: The first phase study was from May to October in 2000 and the second phase study was planned to extend further the shelf-life of the sterile packs from April 2001 to June 2002. Six hundred and fourty packs containing small gauze with four wrapping materials(100 times and 50 times washed two-ply reusable cotton, disposable craft paper, and disposable new pouch bag) and the 104 returned set after their shelf-life were stored on the top or middle of shelves or closed cabinets and storage durations from 1 to 20 weeks in the first phase study. The test packs were collected weekly and cultured in the laboratory. Five hundred seventy-six test packs were prepared with three wrapping materials (except 50 times washed cotton and returned set) and stored in the same location as the First phase study and collected and cultured monthly after three months storage (from July 2001) for one year in the second phase study. The temperature and relative humidity was monitored whenever the test pack was collected. Results: The gauze in the test packs were not contaminated until 154 days in the first study phase and until 423 days in the second phase study. The temperature and relative humidity of storage locations were 25.9degrees C and 55.2% in the first phase study and 26.0degrees C and 45.9% in the second phase study, respectively. Conclusions: There was no difference in the sterility integrity of the test packs with different wrapping materials. storage locations and environments. and storage durations. It was possible to extend shelf-life from two weeks to three and six months in the study hospital.