The aim of this paper is to describe part of the findings of a study which explored the health visitor's role in identifying and working with vulnerable families in relation to child protection The study was conducted using a broadly qualitative approach A two-stage approach was undertaken to explore the concept of vulnerability and to assess health visitors’ work in this area of practice In stage one a postal survey of 102 health visitors was conducted with a response rate of 58 (57%) In stage two 12 m-depth interviews were completed with health visitors This paper outlines one major aspect of the findings and focuses specifically on health visitors’ perceptions about the concept of vulnerability and its relevance to child protection work The analysis suggests that vulnerability is a nebulous, transient and complex concept influenced by multiple interacting factors The existence of a continuum of vulnerability is clearly evident It appears that families move in and out of vulnerability at various stages of the life cycle and this is largely dependent on‘internal’ and‘external’ stress factors and coping ability This paper contributes to the knowledge base of vulnerability and raises a number of issues for health visiting practice