There is a growing interest in the distinction between grandiose and vulnerable narcissism, along with a hypothesis of a fluctuation between grandiose and vulnerable narcissism within individuals. There are several well-validated measures of both grandiose and vulnerable narcissism, but research has generally found that they are relatively distinct in their relations with their nomological networks. Further, the existing measures of narcissism do not actually assess for a possible fluctuation. The present study developed three scales of narcissistic fluctuation: fluctuation between indifference and anger, grandiosity and shame, and assertiveness and insecurity. Consistent with expectations, the FLUX scales correlated with both grandiose and vulnerable narcissism, displayed convergent and discriminant validity with factor derived-narcissism scales and the five-factor model, and correlated at moderate-to-large effect sizes with measures of affective lability. The three FLUX scales were also reduced to one unidimensional nine-item scale of narcissistic fluctuation (the g-FLUX) that retained the correlational properties for the more specific scales and had incremental validity over the Five-Factor Narcissism Inventory and Pathological Narcissism Inventory grandiose and vulnerable scales in accounting for affective lability. Results from the present study suggest that the FLUX scales may provide an informative assessment of a fluctuation between grandiose and vulnerable narcissism. (PsycINFO Database Record (c) 2018 APA, all rights reserved).