Dimensions of the vulnerable child syndrome are clarified in a critical review of the research and clinical literature. The central construct of the vulnerable child syndrome, an increased parental perception of child vulnerability to illness or injury, is examined in the context of separation and loss. Measures of perceived child vulnerability are reviewed. A new conceptual model of parental perception of child vulnerability is presented that takes into account child, parent, parent-child, parent-clinician, and family factors. Directions for future research are suggested.