The Youth Self-Report Form's (YSR's) factor model was derived from traditional exploratory factor analytical procedures. Assuming appropriate model specification, psychometrically invariant items, and that its items provide useful psychometric information across nations omitted from its normative samples, the YSR is widely used in cross-national studies of nonreferred children. Item response theory analytical procedures reveal (a) 2 dimensions partly overlapping with the YSR's Internalizing and Externalizing second-order factors; (b) variance (i.e., differential item functioning) in how well a few items discriminate for nonreferred children across two nations; and (c) variance in estimating severity levels in children with identical psychopathological severity cross-nationally. Addressing psychometric variance, limiting redundancy, and matching children's psychopathological severity levels with items measuring this severity might promote more accurate and economical assessment. (Contains 2 tables, 6 figures and 4 notes.)