The aim of this article is to examine, by means of an empirical study, the: a) relationship between formal and cultural structures; b) similarities and differences between professional subcultures (medical, nursing and managerial); and, c) the effects of the social assumptions of the work teams on development activities in one large primary health care organization. The results show that different professional groups have created quite different sets of social values, norms and assumptions, which have significant consequences, both for patients care and organizational performance.