This study describes variations in the occurrence of negative middle ear pressures during a 12-month period in an unselected group of 352 children, all about seven years old. During the year-long study, the children were screened several times in the field to measure middle ear pressure and hearing losses greater than 20 dB. The children that failed this field screening were transported to the Hearing Clinic of Vejle Hospital and their auditory acuity was measured by audiological procedures. Calculation of the cumulated incidence of negative middle ear pressure showed that a pressure of -150 to -250 mm H2O, otherwise purported to reflect pathology, occurred in 25% to 55% of the children at different times during the year. The prevalence of these negative middle ear pressures was such as to negate the term "pathology," which is usually applied to such findings. Various negative pressures were found to occur as characteristics of the season of the year and were also found to occur more frequently bilaterally in boys. Conductive hearing losses of 10 to 20 dB were found in 7% to 44% of the children but were not found to be related to sex. The variability of middle ear pressure limits its value in predicting middle ear pathology and leads to a risk that children will be over-referred for further investigation and treatment of nonexistent middle ear problems if middle ear pressure is used as the sole prognosticator of middle ear pathology.