Careless responders are respondents who lack the motivation to answer survey questions accurately. Empirical findings can be significantly distorted when some respondents devote insufficient effort to the survey task, and researchers therefore attempt to identify such respondents. Many measures of careless responding have been suggested in the literature, but researchers frequently struggle with the selection and appropriate use of the available methods. This chapter offers a classification of existing measures of careless responding along two dimensions and presents a conceptual discussion of their relative strengths and weaknesses. An empirical study demonstrates how the various measures can be used to identify careless responders and how these measures are related to each other.