Introductory biology courses for pre-professional majors at large universities are usually high-enrollment lectures with associated labs that complement the lecture, but are independently taught and administered. Although web-based instructional formats have become popular alternatives to traditional lectures, it is unknown how these formats affect laboratory performance. To test for effects of hybrid formats on laboratory performance, we conducted a teaching experiment. Students taking an introductory biology course enrolled in either a traditional format lecture or a hybrid (part lecture, part online) lecture. We used laboratory scores and performance on common final exam questions to assess laboratory and lecture performance, respectively. Overall, laboratory performance did not differ between students in the hybrid vs. the traditional lecture, but we did observe a significant interaction between minority status and course format. Minority students in the hybrid lecture scored higher in laboratory relative to nonminority classmates. Minorities in hybrid formats may have benefited more from general characteristics of online homework (e.g., learned more actively, improved general problem-solving skills like those used in laboratory). Or, minorities may have benefited because online components may have created a more balanced social atmosphere or helped offset negative effects of lower computer and internet availability in some minority groups. Hybrid course designs and online instructional components may help narrow performance gaps between minorities and nonminorities. We caution, however, that minority students in the hybrid lecture performed worse than classmates on common lecture exam questions (despite laboratory improvement). Hybrid course designs should be implemented cautiously until more research is completed. (Contains 4 figures and 1 table.)