The construct of stress reactivity refers to the disposition of a person to answer stressors with immediate, intense, I and long lasting stress reactions. Stress reactivity is assumed to be determined by a disadvantageous pattern of four personality characteristics: high intrusiveness, low self-efficacy, high arousability of the central nervous system, and high negative affectivity. The Stress-Reactivity-Scale (SRS), which is presented in this article, does not only assess the general stress reactivity but also measures stress reactivity in different stressor domains. Item-test correlations and reliability coefficients as well as the test score distributions meet the test-statistical demands (N = 975). Concerning the validation of the SRS, I findings regarding the factorial validity and correlations with other construct-related personality traits, bodily complaints, steep behavior, chronic diseases, and cortisol reactions in a laboratory stress study are reported. Additionally, findings from a twin study on the influence of genetic factors on self-reported stress are reported, and finally sex differences are described. The results underline the validity of the SRS. The questionnaire is suitable for clinical research, to assess individual differences in stress reactivity, and as a tool to evaluate stress management programs.