Research suggests there are differences in children's internalizing and externalizing symptoms as a function of age, race, sex, and socioeconomic status (SES). Males, Black children, and children experiencing lower SES have been rated as having more externalizing problems. Female and older children have been rated as having higher internalizing symptoms. The validity of these findings rests on the assumption that the measures mean the same thing across groups and developmental time (i.e., measurement invariance [MI]). Without assuring MI, results may represent differences in measurement and not true differences in the underlying construct. The Strengths and Difficulties Questionnaire (SDQ) is a widely used tool to measure internalizing and externalizing symptoms. Papers have evaluated MI of the SDQ in school-aged children. However, to our knowledge, no studies of young children have examined MI across Black and White families from diverse SES backgrounds. Data from the