There is much controversy about the treatment of Lyme disease with respect to 2 poorly defined entities: "chronic Lyme disease" and "posttreatment Lyme disease syndrome." In the absence of direct evidence that these conditions are the result of a persistent infection, some mistakenly advocate extended antibiotic therapy (>/=6 months), which can do great harm and has resulted in at least 1 death. The purpose of this brief report is to review what is known from clinical research about these conditions to assist both practicing physicians and lawmakers in making sound and safe decisions with respect to treatment.