The Automated Surface Observing System (ASOS) makes extensive use of software and firmware throughout its data collection and processing chain. This system collects data on surface weather at over 800 locations sponsored by the National Weather Service, the Federal Aviation Administration, and the Department of Defense. Data from ASOS are used by pilots, air traffic controllers, air line dispatchers, forecasters and climatologists. Significant efforts have been made to ensure that ASOS and related data processing and display systems are free of Y2K-related software problems. This paper will describe those efforts and the resultant findings.