This study examined the effect of primary stimulus level on the ability of distortion product otoacoustic emission (DPOAE) measurements to separate normal-hearing from hearing-impaired ears. Complete I/O functions were obtained for nine f2 frequencies on 210 people approximately evenly divided between normal hearing and hearing impaired. Clinical decision theory was used to assess both DPOAE amplitudes and DPOAE threshold as diagnostic indicators of hearing status. Moderate level primary stimuli elicited responses that separated normal from impaired better than either lower level or higher level stimuli. The two populations were differentiated for all frequencies above 500 Hz by DPOAE amplitude, given primary levels, L1 and L2, of 65 and 55 dB SPL. DPOAE threshold performed equally well, but threshold ambiguity in noise and longer testing times make it a less suitable DPOAE measure to use diagnostically.