Affective instability (AI) is as a central component of a number of psychiatric disorders, but it has received relatively little empirical attention as an individual construct. The goal of the current study was to study AI in the context of a broad empirical network of relevant constructs and compare its pattern of relations with those generated by trait neuroticism, both of which were assessed using both self- and informant reports. In a sample of 343 college students, the present study examined the correlations generated by an AI factor (derived from a factor analysis of relevant scales) in comparison to neuroticism in relation to personality and etiological and outcome variables. An exploratory factor analysis revealed a one-factor structure of AI related to the experience of intense and changeable negative affect and subsequent physical and behavioral consequences. The correlations generated by self- and informant reports of AI with these external criteria were almost perfectly correlated with the correlations demonstrated by self- and informant reports of neuroticism. Self- and informant reports of AI generated a pattern of results consistent with its role in a number of psychological disorders that are associated with substantial impairment. The current data suggest that AI might be best conceived of as largely overlapping with neuroticism rather than as a distinct construct.