The initial prodrome in psychosis is potentially important for early intervention, identification of biological markers, and understanding the process of becoming psychotic. This article reviews the previous literature on prodrome, including descriptions of symptoms and signs, and patterns and durations of prodromes in both schizophrenic and affective psychoses. Early detailed descriptions, achieved through mainly anecdotal reports, are compared with current conceptualizations, such as the DSM-III-R checklist of mainly behavioral items, which seeks to enhance reliability of measurement but at the expense of adequately describing the full range of phenomena. Current confusion about the nature of prodromal features and concerns regarding the reliability of their measurement are highlighted. This article proposes an alternative model for conceptualizing prodromal changes (the hybrid/interactive model) and discusses the different ways to view this phase. The need for a more systematic evaluation of the prodromal phase in first-episode psychosis is emphasized.