Open-ended investigative work is important for science at the high school level because it provides students with experiences approaching the authentic practice of scientists. In England context, some teachers provide opportunities for open-ended investigation, even though at post-16 (pre-university) A-Level they are no longer required to do so. This qualitative study had two aims: to identify teachers' intended learning outcomes for open-ended investigations and to understand the different ways that teachers perceive, interpret and teach open-ended investigative projects. Questionnaires (n = 17) and in-depth, semi-structured interviews with high-school teachers (n = 12) were used. Analysis of questionnaire data suggested five 'key ideas' related to teachers' intended learning outcomes for open-ended investigations: state of the field, research design, data handling, iteration, and 'real' science. Interviews revealed repertoires for addressing learning relating to each of these key ideas. Phenomenographic analysis of interview data suggested six qualitatively different ways of perceiving open-ended investigation, which corresponded to different emphases for student learning: the teacher-scientist, the teacher-inquirer, the instrumentalist, the independence-builder, the scaffolder and the personal developer perspectives. The findings are expected to be useful for informing teacher professional development and reflection, and for those developing curricula, teaching materials or assessments involving open-ended investigation.