This paper analyzes the potential uses of the Survey of Income and Program Participation (SIPP) in tracking outcomes across different disability definitions in various SIPP panels. Our findings illustrate the importance of exercising caution when measuring disability trends. We find that the timing and structure of specific questions affects disability prevalence rates and, hence, influences observed outcomes. When we use comparable definitions across panels, we consistently find that employment of men with disabilities has fallen from 1990 to 1996 and the employment rates of women with disabilities has remained flat across a variety of disability conceptualizations. While there are some important concerns regarding the measurement of disability, we believe the consistency of our results across a variety of definitions illustrates an important and disturbing trend. Given that these definitions are commonly used in several policy studies, including several recent studies on the Americans with Disabilities Act (ADA), it is important for researchers and survey designers to understand these issues.