Purpose: This article describes the development and evaluation of The University of Western Ontario (UWO) Plurals Test, which is an English language measure of detection of the word-final fricative cue for plurality. Method: Normative data are provided for 26 listeners with normal hearing and 24 listeners with hearing impairment (children and adults), as are evaluations of the acoustical properties of the stimuli, the test's test-retest reliability, and the test's sensitivity to changes in hearing aid signal processing (e.g., nonlinear frequency compression). Results: Results indicate reliable, repeated outcome measurement at the level of the individual. When compared to a global measure of real-world listening preference, the UWO Plurals Test was found to be somewhat sensitive to the effects of changes in hearing aid signal processing. Conclusion: Findings suggest potential use of the UWO Plurals Test to evaluate aided and unaided ability of listeners between the ages of 6 and 81 years to detect the wordfinal fricatives /s/ and /z/ as they occur in English plural nouns. © American Speech-Language-Hearing Association.