Objective: The purpose of this study was to determine syncytiotrophoblast intercellular adhesion molecule- 1 expression in villitis and in normal chorionic villi from term (37- 42 weeks of gestation) placentas with or without villitis. Study design: A cross-sectional study was conducted to determine syncytiotrophoblast intercellular adhesion molecule- 1 expression in villitis (n = 16) and in normal villi from placentas with or without villitis (n = 16). Villitis was diagnosed with antibodies to human leukocyte antigen- DR and CD3 and hematoxylin and eosin staining of serial sections; intercellular adhesion molecule- 1 reactivity in syncytiotrophoblast was confirmed with antibodies to intercellular adhesion molecule- 1 and cytokeratin. Results: Villitis lesions had higher syncytiotrophoblast intercellular adhesion molecule- 1 expression than normal chorionic villi from placentas with (19.9% vs 3.5% villi; P < .001) or without (19.9% vs 0.31% villi; P < .001) villitis. Normal villi from placentas with villitis had higher syncytiotrophoblast intercellular adhesion molecule- 1 than villi from placentas without villitis (3.5% vs 0.31% villi; P <.001). Conclusion: Placentas with villitis have significantly more syncytiotrophoblast intercellular adhesion molecule- 1 expression than placentas without villitis. The finding that normal villi from placentas with villitis have more syncytiotrophoblast intercellular adhesion molecule1 than normal villi from placentas without villitis suggests that syncytiotrophoblast intercellular adhesion molecule- 1 could be the first step in villitis development. Objective: The purpose of this study was to determine syncytiotrophoblast intercellular adhesion molecule- 1 expression in villitis and in normal chorionic villi from term (37-42 weeks of gestation) placentas with or without villitis. Study design: A cross-sectional study was conducted Villitis was diagnosed with antibodies to human leukocyte antigen- DR and CD3 and hematoxylin and eosin staining (n = 16) and in normal villi from placentas with or without villitis of serial sections; intercellular adhesion molecule-1 reactivity in syncytiotrophoblast was confirmed with antibodies to intercellular adhesion molecule-1 and cytokeratin. Results: Villitis lesions had higher syncytiotrophoblast intercellular adhesion molecule- 1 expression than normal chorionic villi from placentas with (19.9% ​​vs 3.5 % villi; P <.001) or without (19.9% ​​vs 0.31% villi; P <.001) villitis. Normal villi from Placentas with villitis had higher syncytiotrophoblast intercellular adhesion molecule- 1 than villi from placentas without villitis (3.5% vs 0.31% villi; P <.001). Conclusion: Placentas with villitis have significantly more syncytiotrophoblast intercellular adhesion molecule- 1 expression than placentas without villitis The finding that normal villi from placentas with villitis have more syncytiotrophoblast intercellular adhesion molecule1 than normal villi from placentas without villitis suggests that syncytiotrophoblast intercellular adhesion molecule- 1 could be the first step in villitis development.