Background: Despite its value as a diagnostic measure of middle-ear function, recommendations for tympanometry as a screening test for middle-ear disorders have been tentative. This is primarily due to concerns related to over-referrals, cost-effectiveness, variability in referral criteria and protocols, variable reported screen performance, and influence of demographic and environmental factors. Purpose: The current study assessed tympanometry in a large population of children between 5-7 yr old in terms of normative ranges, performance of current recommended referral criteria, and associations with independent demographic and environmental variables. Research Design: Retrospective cohort study. Study Sample: A total of 2868 children and their families were originally enrolled in the Raine Cohort. Study in Western Australia. Of these, 1469 children between 5-7 yr old (average age 5 5.97 yr, SD 5 0.17 yr) were evaluated with tympanometry and pure-tone audiometry screening. Data Collection and Analysis: Tympanometry was conducted using a 226 Hz probe tone with screening ipsilateral acoustic reflexes recorded using a 1000 Hz stimulus. Hearing screening was conducted using pure tones at 20 dB HL for 1000, 2000, and 4000 Hz. Relationships among normative ranges (90% and 95% ranges) for tympanometric indices, age, gender, and month of test were determined. Associations were also explored between tympanometry referrals and month of test, gender, and absence of acoustic reflexes. Results: Normative 90% ranges for tympanometric peak pressure was -275 to 15 daPa, 60-150 daPa for peak compensated tympanometric width, 0.2 and 1.0 mmho for peak compensated static admittance, and 0.7-1.3 cm3 for ear canal volume. Current screening guidelines result in high referral rates for children 5-7 yr old (13.3% and 11.5% using the American Speech-Language-Hearing Association [ASHA] and American Academy of Audiology [AAA] guidelines, respectively). The subgroup of children 6-7 yr old had referral rates (for ears tested) of only 3.3% and 2.7%, respectively, according to ASHA and AAA guidelines. The prevalence of middle-ear effusion (admittance ,0.1 mmho) was significantly different across seasons, with the highest (13.5%) in September and lowest (3.8%) in January. Month of test was associated with a general decrease in tympanometric peak pressure across the population. Conclusions: An 80% reduction in tympanometry referrals for children ages 6 and 7 yr compared with children age 5 yr argues for tympanometry as a first-tier screening method in older children only. The impact of regional seasonal influences, representing an increase in referrals as high as 3.5 times from one month to another, should also inform and direct pediatric screening programs for middle-ear functioning and/or hearing loss.