Goals: To validate cut-off values of CD 3+ T-cell receptor gammadelta chain (TCRγδ + ) intraepithelial lymphocyte (IEL) in the (differential) diagnosis of celiac disease (CD). Background: CD is characterized by an increase in gamma-delta IEL (CD 3+ TCRγδ + IEL). Study: Percentages were determined by flow cytometric analysis of IELs from small bowel biopsies in 213 CD and 13 potential CD (PCD) patients and in total 112 controls. A cut-off value for percentages of CD 3+ TCRγδ + IEL to differentiate active CD and controls was obtained from a receiver operating characteristic curve and implemented in controls and PCD patients. Results: Percentage of CD 3+ TCRγδ + IEL was significantly increased in the majority of CD patients, irrespective of the presence of villous atrophy. A cut-off value of 14% for CD 3+ TCRγδ + IEL resulted in 66.3% sensitivity and 96.6% specificity for CD diagnosis (area under the curve, 88.6%). Conclusions: A percentage of ≥14% CD 3+ TCRγδ + IEL has a high specificity for CD diagnosis and can be of diagnostic help in cases where diagnosis is not straightforward.