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These charts were developed in the Orthoptic Clinic at Northwestern University, which has been supported by grants from the Knapp Memorial Fund and the American Academy of Ophthalmology and Otolaryngology. They consist of fourteen double test charts for diagnosis and thirty-three pairs of split charts for training. They are for use in any standard stereoscope, a special holder being provided for the split charts. These utilize the principle of Sattler's charts, the cards being reversible, so that the opposite effect of depth may be obtained on reversal. This makes it impossible for children to learn the relative position of objects in the charts. The distance between the charts may also be varied, so that a series of settings resembling the H and I series of Wells may be obtained with each pair. All the charts, when fused, show definite relief, which makes them more easy to fuse than the