The Lagopedo experiments were the first in situ ion composition measurements of a chemically modified ionosphere. An artifical ionospheric hole was produced by the injection of H2O and CO2 into the O+ dominant F2 region. These released chamicals increased the natural ionospheric depletion rate by approximately two orders of magnitude by changing the rate of molecular ion formation. As the rocket payload passed through the event cloud O+ was observed at a reduced density, and H2O+, H3O+, and O2+ were observed in enhanced amounts that varied with time after and distance from the event. H3O+ was dominant at times immediately after the event, when the neutral water density was high, but rapidly decreased to 20-40% of the H2O+. A computer model simulated the postevent O+ and O2+ distributions well, but it had mixed success with the H2O+ and H3O+ distributions. Measureable changes in ion composition levels were detected up to 40 km from the release point.