The purpose of this study was to investigate the beliefs of six experienced high school science teachers about (1) what is successful science learning; (2) what are the purposes of laboratory in science teaching; and (3) how inquiry is implemented in the classroom. An interpretive multiple case study with an ethnographic orientation was used. The teachers' beliefs about successful science learning were substantively linked to their beliefs about laboratory and inquiry implementation. For example, two teachers who believed that successful science learning was deep conceptual understanding, used verification labs primarily to illustrate these concepts and used inquiry as a type of isolated problem-solving experience. Another teacher who believed that successful science learning was enculturation into scientific practices used inquiry-based labs extensively to teach the practices of science. Tension in competing beliefs sets and implications for reform are discussed. ? 2004 Wiley Periodicals, Inc. J Res Sci Teach 41: 936-960, 2004.