Objectives.Analyses were performed to reproduce and examine the sensitivity of the cross-specialty linkage algorithm used by Hsiao et al1to obtain the currently implemented resource-based relative value scale for Medicare physician reimbursement.Methods.The cross-specialty linkage procedure designed and implemented in Hsiao et al is an important component of the resource-based relative value scale underlying current Medicare Fee Schedule. This linkage procedure aligns independent intraspecialty relative value scales onto a common scale, and therefore determines the level of reimbursement accruing to each specialty. The complexity of the algorithm to perform this alignment has prevented critical review of the methodology. The authors examine the statistical properties of the algorithm, and diagnose its sensitivity from changes in the data and small modifications to the numerical procedure.Results.Our examination of the linkage algorithm uncovered some issues requiring further consideration. These include the questions raised about the use of "biweighting," and about the benefits of incorporating correlation information into the analysis. Moreover, simulation analyses demonstrate that the existing relative value scale is sensitive to changes in the input data and methodology. Certain specialties' reimbursement can shift by as much as 32% using Hsiao's algorithm. Most importantly, the interspecialty linkage algorithm underlying the current fee schedule downweights pairs of linked services even when such links are deemed more important from a clinical point of view. As a result, in some cases clinically superior links received little or no importance in the algorithm.Conclusions.The cross-specialty linkage procedure described in Hsiao et al may not adequately perform the task of aligning intraspecialty relative value scales onto a common scale because of the sensitivity of the algorithm and the choice of statistical methodology. The authors suggest improvements to Hsiao's method resulting from our analyses. If widespread adoption of the Medicare Fee Schedule is a component of health care reform, reconsideration of the process determining each specialty's payment level assumes new importance.