The most recent New Zealand national curriculum development in Science occurred between 1991 and 1993. This Science curriculum placed value on students developing scientific investigative skills. The senior Biology curriculum for students in Years 11 - 13, developed to link with the Science curriculum, restated the Science curriculum’s investigative emphasis. With this new emphasis on the investigative approaches to learning school Science by national curriculum policy, it became important to identify how teachers may help their students to achieve the investigative objectives; to determine ways to support Biology teachers when they are introducing openness into their programmes; and to identify perceived benefits and constraints related to the introduction of investigative activities. This study explores the nature and role of practical work, including investigative approaches, in school science. It reviews the purported functions of, and degree of intersection between, problem solving and investigative approaches to learning in science. After an exploration of competing views of learning, scientific investigative problem solving practical work is placed within a framework of a co-constructivist pedagogy. There were three main phases in the data gathering for this study. The first two phases of this research project were conducted within a large, urban, co-educational, state secondary school. All of the school’s Biology teachers participated in the initial introduction of investigative practical work and one of these teachers worked with additionally developed material for a second year. A teaching package relating to the introduction of partially open investigative practical work was developed during 1994. Teachers from other secondary schools from around New Zealand participated in the third phase trial of this material. The research findings present challenges to a growing rhetoric regarding the value of open investigative practical work in school science. The introduction of partially open investigative practical work into a Year 12 Biology programme was found to be exacting of the teachers and students. The students required deliberate and focussed teaching if they were to progress their scientific inquiry skills. The students valued the opportunity to have more control over the direction of their practical work. They found investigative work motivating and claimed that it increased their learning. Some students accepted the opportunity for personal involvement, self-direction and responsibility very quickly, whilst others needed ongoing support and encouragement. The teachers acknowledged a cognitive and affective value for investigative practical work in a Biology programme but reported considerable difficulties with the introduction and assessment of such a programme. Implications for both classroom practice and teacher development emerge from this study. Suggestions of ways to help students to carry out investigations, to better hypothesise, and to plan and gather data are given, as are strategies to help students critique their work. It is suggested that teacher development programmes include opportunities for teachers to develop their own understandings and skills in relation to investigative science. There could also be an emphasis on pedagogical practices which may enhance students’ learning in this regard. Time, personnel, equipment and materials resource implications may need to be addressed.