A model for predicting ammonia losses during sprinkler application of animal wastes was developed. These losses are important because of the cost of nitrogen as a fertilizer and because it is a potential pollutant. A single launched droplet was modelled and a computer program developed to simulate the resulting trajectory and evaporation losses. Losses from the average droplet were then expanded to calculate losses for the entire sprinkler system. The model requires 13 independent input variables: ambient air temp. RH, atmospheric pressure, horizontal and vertical components of wind speed, initial spray velocity, horizontal and vertical components of spray direction, nozzle height and pressure, droplet diam., ammonia concentration and pH. Based on these, all dependent quantities are determined within the program. The model developed predicted ammonia losses consistent with field data collected for pig lagoon effluent. Comparison of model predictions with data collected in previous studies of sprayed fertilizers showed close agreement of the ammonia loss variation with pH.