Workers Compensation presents a mixture of a substantial majority of medical only claims with less numerous, but much more variable, indemnity (lost-time) claims. Some indemnity claims can remain open for decades, with significant implications for the duration of time over which loss amounts are paid and/or identified and the potential emergence of losses long after the original accidents occurred (i.e., in the loss development "tail".) There are differing levels of data and information available to estimate this “tail” for actuaries making various projections. In this session we will define the problem, review some historical loss development experience and discuss various approaches taken by actuaries at insurance companies, consulting firms and workers compensation rating bureaus to the challenges of estimating loss development in the tail, including a recent analysis of a large body of relevant data spanning over 70 years.