<p>The widespread use of channelization for agricultural drainage has resulted in the presence of numerous channelized agricultural headwater streams in the Midwestern United States, Canada, and Europe. Channelization results in the removal of instream wood that is a critical instream habitat feature. Quantitative information on instream wood characteristics within channelized agricultural headwater streams and how they compare to unchannelized streams is limited. We assessed the diversity, frequency of occurrence, and the amount of large instream wood within channelized and unchannelized agricultural headwater streams within a large Ohio watershed by conducting a small-scale field study and a retrospective analysis of a large-scale instream wood database. Our field study documented that the amounts of large instream wood in agricultural headwater streams in central Ohio was similar to the values documented in other Midwestern headwater streams. Our field study also quantified that the diversity and amounts of large instream wood was greater in unchannelized than channelized streams. Our retrospective analysis observed that large instream wood diversity and percentage of sites with logs, root wads, and root mats were greater in unchannelized than recovering or recently channelized sites. Our results and others from the Midwestern United States quantify that stream channelization for agricultural drainage reduces the richness and amounts of large instream wood to at least 1/2 that of values observed in unchannelized headwater streams. These results suggest channelized agricultural headwater streams may benefit from watershed management strategies that increase the diversity and amount of large instream wood within these degraded streams.</p>