This issue of Physician Assistant Clinics, Guest Edited by Jane McDaniel of Yale University, is devoted to Laboratory Medicine. Articles in this issue include: Rheumatology; Sexually Transmitted Infections; Provider Performed Microscopy Procedures; New Methods in Dementia Testing; Cardiology Testing; Thyroid Testing; Renal Function Testing; Anti-Xa for Heparin Monitoring and other Coagulation Studies; ABG Interpretation; Transfusion Medicine; Diagnostics for WBC Abnormalities: Leukocytosis/Leukopenia; Anemia Diagnostics for Iron Deficiency, B12/Folate Deficiency, Thalassemias, and Anemia of Chronic Disease; Hematology Testing for Hemolytic Anemias; and Liver Function Testing.