This study examined the applicability of the Psychopathy Checklist: Youth Version (PCL:YV; Forth, Kosson, & Hare, 2003) among a large sample of serious offending adolescent males. Adopting an item response theory approach, item properties of the PCL:YV were examined using the generalized partial credit model. Results showed that need for stimulation, "irresponsibility," and callous & unemotional were sensitive to changes in respondents' varying psychopathy levels, whereas lack of realistic, long-term goals; superficial charm; and revocation of conditional release were less so (quoted PCL:YV item published with permission by Multi-Health Systems, Inc.; see full permissions statement in footnote 1 in the article; other items are paraphrased). Substantial differential item functioning was also found in 15 of the 20 PCL:YV items among Caucasian, African American, and Hispanic offending boys, indicating that item functioning was not invariant across race/ethnicity. Questions remain regarding whether the construct of psychopathy as assessed with the PCL:YV is equivalent across adolescents in general and across different race/ethnic groups in particular.