Evidence supporting the application of Brown's (1991, 1993) conception of behavioural addiction to computing behaviour is presented. Questionnaire items tapping Brown's addiction criteria were factor-analysed along with others, including computer apathy-engagement and computer anxiety-comfort items of Charlton and Birkett (1995). Items relating to some of Brown's criteria (tolerance, euphoria, and cognitive salience) were found to be complex, an Addiction factor loading upon them but an Engagement factor loading more highly. Items tapping other criteria (conflict, withdrawal, behavioural salience, and relapse and reinstatement) were shown to be factor pure, with only the addiction factor loading highly upon them. It is concluded that Brown's conception of behavioural addiction can be applied to computer-related behaviour, although the relationship of milder facets of addiction, which are also merely indicative of high engagement, to computer-related addictions is non-unique. It is also concluded that classifying individuals as exhibiting pathological computer use using checklists based upon adaptations of DSM criteria for pathological gambling is likely to overestimate the number of people addicted to computing activities.