Because the state of our knowledge of many aspects of the etiology and pathogenesis of otitis media and related conditions is deficient, precise characterizations of certain aspects of the disease may not be possible. In fact although most studies in the past have failed to define the specific disease state to be investigated, the specific type of otitis media or related condition to be studied must be as clearly defined as is clinically possible in order for any prospective study of otitis media to be valid. The state of the art of the presently available methods to identify these conditions also poses certain limitations; at present, there are five methods to identify otitis media and related conditions: history, audiometry, tympanocentesis/myringotomy, otoscopy (including otomicroscopy), and impedance measurements (tympanometry and assessment of the middle ear muscle reflex), and they all have inherent elements of unreliability. Historical information obtained from parents or the child is usually unreliable; a positive history may aid in defining the problem, but a negative otologic history does not rule out the presence of otitis media since it is frequently asymptomatic. Audiometry has been shown to be a poor method of identifying otitis media. Although tympanocentesis or myringotomy is the most reliable way to identify otitis media with effusion (OME), it is invasive, frequently requires an anesthetic, and is usually a confounding variable. In an effort to establish the diagnostic value of otoscopy, tympanometry, and the presence or absence of the middle ear muscle reflex in identifying OME, the diagnostic findings by these three methods were compared with the findings at myringotomy in 239 children (425 ears). The study showed that even experienced clinicians had some difficulty in identifying those ears with effusion (sensitivity) and had even greater difficulty in making a diagnosis of those ears without an effusion (specificity). Tympanometry employing patterns that have been validated with myringotomy findings was found to be as accurate as expert otoscopy. On the other hand, the presence or absence of the middle ear muscle reflex was found not to be a useful method of diagnosing the presence of OME due to its extremely low specificity. An algorithm derived from the combination of the three methods had highest sensitivity and specificity. From this study, the following recommendations regarding the identification of OME are suggested. All investigators who employ otoscopy should be validated by comparing their assessments either with the findings at myringotomy or with a previously validated otoscopist. Interobserver reliability of all otoscopists should be established prior to and maintained during clinical studies of OME. Only electroacoustic impedance instruments in which the tympanometric patterns have been validated should be used. Tympanometry employing validated tympanometric patterns has a high degree of sensitivity and specificity, and as such can provide an objective method to identify OME. Middle ear muscle reflex measurements should not be used as the only method to identify OME. An algorithm that includes otoscopy, tympanometry, and, to a lesser degree, the middle ear muscle reflex measurement should be employed for research purposes when a noninvasive method to identify OME is required.