In a previous study among 22 Dutch hospitals many gaps in the care for patients with non-Hodgkin's lymphomas (NHL) were found, compared to best evidence as described in guidelines. In a problem analysis study, barriers and facilitators for good quality of NHL-care were assessed and a tailored implementation strategy was developed, based on these findings. The proposed study aims at the effectiveness, feasibility and costs of this tailored strategy to improve quality of care for patients with an NHL in a clustered randomized controlled trial in 19 Dutch hospitals.