The response of the National Oceanic and Atmospheric Administration multilayer inferential dry deposition velocity model (NOAA-MLM) to error in meteorological inputs and model parameterization is reported. Monte Carlo simulations were performed to assess the uncertainty in NOAA-MLM deposition velocity Vd estimates for ozone (O3), sulfur dioxide (SO2), and nitric acid (HNO3) associated with measurements of meterological variables (including temperature, humidity, radiation, wind speed, wind direction, and leaf area index). Summer daylight scenarios for grass, corn, soybean, oak, and pine were considered. Model sensitivity to uncertainty in the leaf area index (LAI), minimum stomatal resistance, and soil moisture parameterizations was explored. For SO2 and HNO3, instrument error associated with the measurement of wind speed and direction resulted in the greatest Vd error. Depending on vegetation type, the most important source of uncertainty due to instrument error for the Vd of O3 was LAI. Of the model parameterizations studied, accurate estimation of temporal aspects of the annual LAI profile and the characterization of soil moisture supply and demand are most important to model-estimated Vd uncertainty. Considered individually, these factors can result in SO2 and HNO3Vd estimate uncertainty of ¿25% and O3 estimate uncertainty greater than 60%. For single plant species settings, reductions in estimate uncertainty should be possible with minor algorithmic modification, inclusion of more species-appropriate LAI profiles, and careful application of remote sensing technology. ¿ 2000 American Geophysical Union