In this study, we investigated gender and minority achievement gaps on 8th-grade science items employing a multilevel item response methodology. Both gaps were wider on physics and earth science items than on biology and chemistry items. Larger gender gaps were found on items with specific topics favoring male students than other items, for example, an earth science item requiring visual-spatial ability. Minority students were more likely than White students to score lower on harder constructed-response (CR) items. Some teachers were more likely to reduce minority achievement gaps on easier CR items than other teachers. Implications for instruction in terms of improving visual-spatial awareness, efficacy of female students, and modeling scientific literacy for minority students were discussed.