The WINDII instrument onboard the UARS satellite made many thousands of measurements of the apparent brightness of the hydroxyl airglow as a function of tangent height during the night. The measurements were mainly at latitudes between 42°S and 42°N. Most of the profiles of volume emission rate indicate a simple layer with a peak between 85 and 90 km. However, from 5 to 25% of the measured profiles have a more complex structure for the layer profile, most frequently with two peaks separated by 4 to 6 km. The horizontal extent varies from 200 to several thousand kilometers, and the duration may be as long as 1½ hours. Here the WINDII data from November 1991 to April 1995 are used to study the frequency of occurrence of the double‐peaked layers as a function of latitude, season, and local time and to explore possible causes of the unusual profiles. Early in the night the double‐peaked layers occur preferentially at low to medium latitudes, migrating toward the equator by midnight where they remain for the rest of the night. There is a pronounced asymmetry between the hemispheres which reverses between the March/April equinox and the September/October equinox. The solstice behavior is similar, though not so pronounced. Through simulation three possible causes to the observed OH* double‐peaked layers were identified. Gravity waves are a likely source of isolated small‐scale events but the large horizontal scale, long‐duration structures are more likely to result from temperature inversion layers or mixing events or a combination of the two.