Adie's syndrome is a disease of unknown etiology. We known where the damage is, and which nerves are involved. We even know something of how the nerves react after the damage is done, but we don't known what causes the primary injury. The first step in working a jigsaw puzzle is to getall of the pieces right side up and take a good look at them. Some of the jigsaw pieces handled in this paper are listed below. Some of them are new observations; many of them are old concepts, partly modified and partly made secure by new facts. 1. Not all "tonic pupils" are due to "Adie's syndrome"; some are due to local injury and some to a generalized peripheral neuropathy (Table II). 2. All patients should have serologic tests for shyphilis. In this series one in six had positive serology. 3. The incidence of Adie's syndrome in Iowa in the early 1970's was approximately 4.7 per 100,000 population per year. 4. The prevalence of Adie's syndrome, therefore, was approximately 2 per 1000. 5. The mean age of onset of Adie's syndrome was about 32.2 years (Figure 1A). 6. The sex ratio was 2.6 females to each male. 7. Right eyes and left eyes were involved at approximately the same rate (Figure 2). 8. The incidence of second eye involvement in unilateral cases was about 4% per year during the first decade of the disease (Figure 18). 9. If this rate of second eye involvement (4% per year) persists during subsequent decades, then most Adie's pupils will eventually become bilateral. 10. The incidence of Adie's syndrome in a largely caucasian patient group is independent of iris color (Figure 4). 11. Only 10% of patients with Adie's syndrome had completely normal muscle stretch reflexes. 12. The muscle stretch reflexes in the arms were just as frequently imparied as those in th elegs, but the degree of impariment tended to be more severe in the ankles and triceps. 13. When there was any light reaction remaining in an Adie's pupil, a segmental paralysis of the sphincter muscle could be seen. 14. The near reaction of the pupil was often segmental and frequently involved segments which did not respond to light. 15. The segmental paralysis to light was randomly distributed around the sphincter (Figure 6B). 16. There was some tendency for the sphincter palsy to gradually become worse. This progression was also random (Figure 8). 17. Almost all patients with Adie's syndrome had an accommodative paresis at the time of onset. 18. Reading glasses given to a patient with a fresh Adie's pupil were soon discarded as accommodation recovered (Figure 9). 19. Accomodative effort induced an astigmatism in about half of the eyes with Adie's--presumably the result of a segmental palsy of the ciliary muscle. 20. Tonicity of accommodation was present in about 1/2 of the eyes with Adie's, making it difficut for the patient to maintain a steady level of ciliary muscle tone. 21. An occasional patient complained of brow ache from ciliary spasm with near work. 22. In most patients with Adie's syndrome the ciliary muscle was supersensitive to pilocarpine 0...