Leucocytozoon simondi Mathis and Leger was transmitted artificially to a gosling. Other goslings became infected naturally when exposed beside infected ducks. Negative results were obtained from attempts to transfer L. simondi artificially to ruffed grouse, chickens, turkeys, and pheasants and no natural infections were detected in these birds that were exposed for weeks beside infected ducks. L. sakharoffi Sambon could not be transmitted artificially to ducks, chickens, or a pigeon.