CMS has posted its new and reconsidered Medicare clinical laboratory fee schedule (CLFS) codes and preliminary payment determinations for calendar year 2013. Notably, it is CMS’s preliminary determination to set payment for those new Tier 1 and Tier 2 molecular pathology procedures codes reimbursed under the CLFS using the gap-fill mechanism rather than through cross-walking (although CMS has raised the possibility of paying for some or all new molecular pathology codes under the Medicare physician fee schedule rather than the CLFS).