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Chapter 4138mid-frequencies. Of those with hearing loss, sensorineural loss was most common (n=14, 35.9%). Because of missing bone conduction thresholds, that were not measured at 6 and 8 kHz, the type of hearing loss could not be established in 18 adults (46.2%). The audiometric configuration that was observed most, was flat (n=27, 45.0%, Figure 1).Figure 1. Audiometric configurations of 60 adults with 22q11.2 deletion syndrome.Audiometric configurations were mostly flat (45%), or high-frequency steeply (23.3%) or gently(18.3%) sloping. Dotted horizontal line represents the threshold for normal hearing at 20 dB HL. dB HL=decibel hearing level, kHz=kilo Hertz.Plots of individual sensory thresholds against the 90th and 50th percentile of normative data showed that the majority of adults with 22q11.2DS performed worse than the 90th percentile (Figure 2). For the mid-frequency of 1 kHz, 52 adults (86.7%) scored worse than the 50th and 25 (41.7%) scored worse than the 90th percentile of normative data. At 8 kHz, 56 adults (93.3%) scored worse than the 50th percentile and 55 (91.7%) had sensory thresholds above the 90th percentile. TympanometryTympanometry was performed in 24 adults (40.0%) for the better-hearing ear. Most (n=13, 54.2%) had a normal tympanogram (type A) as per the Jerger classification for adults,14 5 (20.8%) had normal admittance with the