This study aimed to explore lower secondary teachers' negotiation of the meaning of laboratory work in a professional development program. A total of 15 in-service teachers participated in the program. In the program, tensions between key ideas concerning traditional way of addressing laboratory work -- with emphasis on subject content and skills -- versus key ideas concerning laboratory work as a way of imitating aspects of real-world scientific practices -- with emphasis on nature of science as process -- was highlighted. The tensions between these key ideas were used in the program as a starting point to frame group discussions and negotiations among the teachers about purposes of laboratory activities. The participants were grouped into three and audio recordings of group reflections and group interviews were used as sources of data for analysis. The results also showed that there were differences between the groups in how they addressed the processes of meaning making of laboratory work. There were two groups of teachers challenged themselves and each other and developed an explicit awareness of tensions between different objectives of laboratory activities. However, a third group of teachers never did the same way of challenging and there is no indication of explicit awareness of different purposes of laboratory work in the data material from the group.