Marginal values of water us ed in irrigation are needed if water is to be optimally allocated among alternative uses. Cobb- Douglas production function analysis and linear programming methods were studied in this investigation to find their fruitfulness in predicting these marginal values. The theoretical properties of both methods indicate that they are conceptually capable of yielding valid marginal value estimates for irrigation water. Further investigation of the two methods was carried out as an empirical test in the Milford area of Utah . Marginal values of water used for irrigation in that area were estimated by both procedures. Although inviolable criteria for testing the validity of the estimates are not available, imperfect standards or' measure imply that they are sound. Linear programming and Cobb -Douglas production function anal ysis are therefore concluded to be fruitful methods of es timating marginal values of water used for irrigation.