• Increasing numbers of cats are living to old age, and they commonly develop behavioral changes. • The behavioral changes reported most frequently are loss of litter box training and crying loudly at night. • The most typical causes of these problems are cognitive dysfunction syndrome (CDS), osteoarthritis, systemic hypertension (commonly secondary to chronic kidney disease or hyperthyroidism), hyperthyroid - ism (even without hypertension), deafness, and brain tumors. • Almost one-third of cats 11- to 14- years of age develop at least one geriatric-onset behavior problem that appears to relate to CDS, increasing to over 50 percent for cats 15 years of age or older.