The contingent negative variation (CNV), first described by Gray Walter in 1964 as “expectancy wave,” is a slow cortical endogenous potential widely recognized as the electrophysiological signature of a task-specific preparatory state that facilitates the stimulus perception and the required response. Here, we describe the techniques needed to elicit, record, and analyze this event-related potential, extensively used in healthy subjects and many pathological conditions as a valuable tool in describing and understanding the impacts of diseases on cognition. Many functions are sequentially engaged during a typical CNV task, such as anticipatory attention, stimulus discrimination, and motor preparation, and CNV, therefore, represents a trustworthy index of the sensorimotor association linked to these cognitive operations