Yield monitors for cotton pickers are available from various aftermarket manufacturers. Currently, yield monitors utilize optical sensing techniques to estimate seedcotton weight by monitoring light interception in air ducts. This method is fairly accurate once calibrated for a particular variety. The ability of light intercepting yield monitors to accurately estimate yields for different varieties are not well documented. Cotton yield monitors serve as a convenient way to determine cotton yields during a time of year when producers are harvesting and time is limited. Prior to yield monitors, yield was determined with portable scales or boll buggies equipped with load cells. These serve as an accurate means of weighing seedcotton; however, this process is more labor intensive and can cost a producer valuable time during harvest season. Generally, yield monitors are accurate once calibrated for a given variety. However, the sole use of yield monitors to determine yields in replicated on-farm variety tests is common. The objective of this study is to compare yields estimated by currently available yield monitors to actual weights of seedcotton harvested from multiple on-farm replicated variety tests.