Effectiveness of the implementation of Modular Nursing in a medical ward: an experimental study. Introduction. Modular nursing (MN) is recognised as an ideal model of care to improve the quality of care and nurses' satisfaction, far from being optimal with Functional Nursing (FN). Aim. To assess the effectivenes of MN on quality of care and nurses' satisfaction. Methods. The ward was divided in two sections, each with dedicated personnel, in one the MN was implemented while in the other the routine care (FN). The quality of care was assessed with QUALPACS, with structured, non participant observations, on a sample of patients before and after the implementation of the MN; the satisfaction was assessed with focus groups. Results. 244 nurse-patient interactions were observed (83 before and 161 after the implementation of the MN); each observation lasted at least 3 hours. Both teams achieved an improvement, though not significant of QUALPACS scores (MN from 2.12 to 2.30; FN from 2.13 to 2.27), thus the implementation of MN did not improve the quality of care. Health professionals were very satisfied of MN because of the better organization, continuity of care in spite of an extra workload related to completion and updating of clinical and nursing records. Conclusions. The implementation of MN, increased health professionals satisfaction but not the quality of care. The implementation of a different organizative model should be assessed with objective and observable outcomes.