Different tympanometric procedures were compared regarding their reliability and systematic differences in middle ear pressure estimation in healthy adults. In a second part of the study the accuracy of measurement was judged by correlating tympanometric readings, obtained by using the different procedures, with known pressure levels applied after cannulating the mastoid air cell system. There were no significant differences in reliability between the different tympanometric procedures tested (p greater than 0.05). However, forward-backward tracing tympanometry and 'zero sweep rate' tympanometry gave smaller errors in the middle ear pressure estimates than the conventional decreasing pressure sweeps. Forward-backward tracing tympanometry at high sweep rate is recommended both for pressure measurements during physiological studies and in clinical practice.