Neither air-bone gap nor acoustic reflex presence/absence gives an unequivocal indication of abnormality in middle-ear sound transmission. In the present study, a stratified population sample was investigated to examine the interrelationships between these and other parameters of middle-ear status. Of a total of 1725 ears, 1450 had both normal acoustic reflex threshold (ART less than or equal to 100 dB; see text) and air-bone gap (ABG less than or equal to 15 dB); 70 had both abnormal ART and ABG; 160 had abnormal ART but normal ABG; 45 had abnormal ABG but normal ART. Examination of data on tympanic membrane appearance and middle-ear pressure in the latter two groups suggests that ART is a considerably more sensitive indicator than ABG of hearing loss involving middle-ear abnormality, with only a marginally higher rate of false positives. However, a more comprehensive clinical picture is obtained when both ART and ABG are measured.