This paper considers how NHS Direct is affecting demand for primary care in particular out of hours services from GPs. This is reviewed through a three-year study of NHS Direct and HARMONI, the integrated telephone health helpline based in West London. It describes the policy background and development of the services on the site, and some of the outcomes of the HARMONI commissioned research to answer the question "Has NHS Direct increased the workload for HARMONI doctors?".The research adopted both a qualitative and quantitative approach using cross-sectional and longitudinal analysis of the data collected. The analysis of the data reveals the issues as both complex and dynamic in nature. The research shows that while there has been no significant change to the total volume of activity, changes within patient groups or GP practices may be significant. In addition, the changes in organisational arrangements may influence significant changes in referral patterns.This was confirmed for example by the changes described in the interview data on the change in nurses' role from gatekeeper to patient advocate, which happened when they ceased to be employees of the part-time co-op and began to work instead for the 24x7 NHS Direct service.The conclusions drawn are that behavioural and organisational changes are at least as significant as the evidence-based computerised decision support software in changing outcomes in the demand for primary care. Amongst the evidence cited is the different demand pattern of calls experienced by those local GPs not integrated into out-ofhours provision into NHS Direct on the West London site at the time of the study. NHS Direct : managing demand for primary care?