The AVE IV Experiment is described and tabulated rawinsonde data at 25 mb intervals from the surface to 25 mb for the 42 stations participating in the experiment are presented. Soundings were taken between 0000 GMT, April 24, and 1,200 GMT, April 25, 1975. The methods of data processing and accuracy are briefly discussed. Synoptic charts prepared from the data are presented, as well as an example of contact data.