The purpose of this study was to find out: (a) pupils' attitudes towards open-ended science investigations, and (b) the problems that pupils encounter when carrying out such investigations in groups. The study was conducted in a class of 39 primary 6 pupils of mixed ability who carried out four investigations. Data were based on pupils' responses on an attitude survey questionnaire, interviews, video tapes of pupils performing the investigations and field notes. The majority of the pupils liked conducting such investigations. Reasons for positive responses were that the pupils had the freedom to explore and devise their own procedures to find out things that they wanted to know about, they could work together and discuss with friends, the investigations were interesting and it was a valuable learning experience. Reasons for negative responses included the difficulty of coming up with good ideas to design the investigations, and group conflicts. The findings also indicate that group dynamics played an important role in influencing pupils' attitudes towards the investigations.