This article discusses the manipulation and measurement of levels of situational self-focus, which is generally labeled ''self-awareness.'' A new scale was developed to quantify levels of public and private self-awareness. Five studies were conducted to assess the psychometric properties, reliability, and validity of the Situational Self-Awareness Scale (SSAS). The SSAS was found to have a reliable factor structure, to detect differences in public and private self-awareness produced by laboratory manipulations, and to be sensitive to changes in self-awareness within individuals over (...) time and across situations. The SSAS can be used as a manipulation check of laboratory self-awareness manipulations and as a means of assessing naturally occurring fluctuations in public and private self-awareness in order to clarify the relation between self-awareness and other variables (e.g., mood and memory). (shrink)