Motivation – This research deals with the identification of collective production of a safe radiotherapy treatment and its potential assistance through computer-supported environments. It takes place in a large design project involving software companies and cancer institutions. Research approach – This work presents an exploratory analysis of cooperation between the four professionals involved in the production of radiotherapy treatment. Uses and functions of cooperative tools have been outlined through observations and use of the “think aloud” technique. Moreover, first stages of a participatory design process have been set up. Findings/Design – We identify three types of cooperation tools (computer-based tools, including an existing workflow, unformal verbal exchanges, and the patient body) and their main functions are: to produce shareable data between professionals, to share the progress in the construction of a treatment and to share procedures and work practices. Rese...