A new and highly controversial literature argues that the employment of working-age people with disabilities fell dramatically relative to the rest of the working-age population in the 1990s. Some dismiss these results as fundamentally flawed because they come from a self-reported work limitation-based disability population that captures neither the actual population with disabilities nor its employment trends. In this paper, we examine the merits of these criticisms. We first consider some of the difficulties of defining and consistently measuring the population with disabilities. We then discuss how these measurement difficulties potentially bias empirical estimates of the prevalence of disability and of the employment behavior of those with disabilities. Having provided a context for our analysis, we use data from the National Health Interview Survey (NHIS) to compare the prevalence and employment rates across two empirical populations of those with disabilities: one defined by self-reported impairments and one defined by self-reported work limitations. We find that although traditional work limitation-based definitions underestimate the size of the broader population with health impairments, the employment trends in the populations defined by work limitations and impairments are not significantly different from one another over the 1980s and 1990s. We then show that the trends in employment observed for the NHIS population defined by self-reported work limitations are statistically similar to those found in the Current Population Survey (CPS). Based on this analysis, we argue that nationally representative employment-based data sets like the CPS can be used to monitor the employment trends of those with disabilities over the past two decades.