Amendments for reducing odor from open-lot beef cattle feedyards were evaluated in the laboratory. Manure was placed in small Tupperware® containers. Water and amendments were added to the manure surface and the containers were attached to a vacuum pump that continually passed 2.5 L/min of carbon-filtered air over the surface. Eleven different amendments were tested, at two different concentrations, in a series of five experiments. Odor samples were collected 3 times during a 10-day period in each experiment and were analyzed by trained panelists for detection threshold (DT), intensity and hedonic tone. None of the amendments showed any overwhelming evidence of greatly reducing odor from simulated open-lot feedyard surfaces.