Although numerous studies have investigated the diagnostic effectiveness of the Speech Sounds Perception Test, few have investigated the qualities of the test that make it effective. Different writers have suggested that it may be effective because of interference from earlier syllables and items, an inability to understand speech, fatigue or an inability to match letters and sounds. If the effectiveness is due to fatigue or interference, the length of the test (60 items) would contribute to its accuracy. Otherwise, a short form of the test could be as effective. Data from 37 brain-damaged and 21 normal individuals indicated that a 30-item version of the test was slightly more accurate diagnostically than the 60-item form. This suggests that a short form of the test could be used without sacrificing diagnostic accuracy, enabling the clinician to save time in assessing neuropsychological patients.