Four studies investigated the reliability and validity of thin slices of nonverbal behavior from social interactions including (a) how well individual slices of a given behavior predict other slices in the same interaction; (b) how well a slice of a given behavior represents the entirety of that behavior within an interaction; (c) how long a slice is necessary to sufficiently represent the entirety of a behavior within an interaction; (d) which slices best capture the entirety of behavior, across different behaviors; and (e) which behaviors (of six measured behaviors) are best captured by slices. Notable findings included strong reliability and validity for thin slices of gaze and nods, and that a 1.5-min slice from the start of an interaction may adequately represent some behaviors. Results provide useful information to researchers making decisions about slice measurement of behavior.