The factor structure of the Multidimensional Ethics Scale (MES; Reidenbach and Robin: 1988, Journal of Business Ethics 7, 871–879; 1990, Journal of Business Ethics 9, 639–653) was examined for the 8-item short form (N = 328) and the original 30-item pool (N = 260). The objectives of the study were: to verify the dimensionality of the MES; to increase the amount of true cross-scenario variance through the use of 18 scenarios varying in moral intensity (Jones: 1991, Academy of Management Review (...) 16, 366–395); and, to examine the items for measurement precision using item-response theory (IRT) methods. Results of confirmatory and exploratory factor analysis failed to conclusively support the hypothesized 3- (short form) or 5-factor (long form) structure; both instruments were instead dominated by a general factor. Item response theory analyses using Samejima’s (1969, Psychometrika Monograph Supplement 34, (4, Pt. 2)) graded response model revealed that many items in the 30-item pool performed very well, and suggested that a different collection of items be used to form a short-form version of the MES. Our proposed 10-item instrument includes more discriminating items than the 8-item version, and has the added advantage of including two items from each of the five ethical philosophies represented in the original 30-item pool. (shrink)