The Haines Index is used in wildland fire management to evaluate the potential for ‘large and/or erratic’ fire behaviour. Published in 1988 as the Lower Atmospheric Severity Index, it was widely adopted and has become popular among fire managers, especially in the United States. Meteorologists have questioned its validity, however. This study revisits the original publication to consider the scientific basis of the Index. It then examines subsequent studies of the Index’s performance. The original Index formulation is found to be incomplete. Some studies suggest that, nonetheless, there may be some association of the Index with large growth events. Others indicate that the Index can be negatively correlated with growth in some situations. The Index, at present, lacks a scientific basis and the limited studies examining its value are inconclusive. It is unclear whether it would more appropriately be revised or replaced.