This paper reports results from two case studies on teamwork, conducted during 2008-2010. The aim was to use a learning ongoing evaluation approach for studying cross professional teamwork in two different interorganizational projects. The experience of using formative evaluation as a method in case studies is also discussed in the paper. In one case the aim was to develop a regional innovation system within the electronics industry based on the Triple Helix model. The other case focused on cooperation between local industrial organizations and authorities to integrate young unskilled persons in the local labor market. The results show that interorganizational teamwork is a difficult process although the organizations involved are committed to the idea and the subject of cooperation. The results also show that a learning ongoing evaluation process demand a genuine interest to learn from failure and success and a willingness to cooperate with the researcher.