Tracking ED asthma visits is an important part of asthma surveillance, as ED visits can be preventable and may represent asthma control failure (1). When using limited clinical ED datasets for secondary purposes such as public health surveillance, it is important to employ a standard approach to operationally defining ED visits attributable to asthma. The prevailing approach uses only the primary ICDÁ9ÁCM diagnosis (Dx) for the ED visit (2); however, doing so may underestimate the public health impact of asthma. We conducted this pilot study to determine the value of including ED visits with asthma-related Dx in secondary or tertiary positions. For example, for an ED visit with a primary Dx of upper respiratory infection and secondary Dx of asthma, it is possible that the infection triggered the asthma exacerbation and the visit could be attributed to both infection and asthma.