The audiograms of 59 patients who had 15 different types of tubes implanted in a prospective study from 1982 to 1985 were reviewed. The audiograms were analyzed for changes in air and bone thresholds at 250, 500, 1000, 2000, 4000 and 8000 Hz. The first post-operative audiogram was tabulated for all the initial post-operative visits and for only the initial post-operative visits in which the tubes were functioning. The change in pure tone average air conduction showed a range in improvement from 22.1 dB for the Armstrong Grommet Tube to 1.9 dB for the Canoe Tube. A total of 8 tube types showed mean improvements of 10 dB or better. With the exception of the Reuter Bobbin, all mean air conduction thresholds in functioning tubes were below 20 dB. For 5 tubes the mean threshold was less than 10 dB. The Armstrong Beveled Grommet, Donaldson, and Richard's Wing tubes showed the largest improvements in air conduction threshold with mean decreases of 22.1, 18.7 and 18.3 dB, respectively. Pure tone average bone conduction for all functioning tubes improved 2.8 dB.