This prospective study was conducted at Ankara University Veterinary Faculty Department of Internal Medicine. The study group was evaluated to one hundred geriatric dog patients that consisted of 52 male and 48 females having similar body weight and age group. The subjects were divided intofour groups in terms of body weight. Group 1 defined as body weight below 10 kg (n=59), group 2 defined as body weight 10-24.9 kg (n=20), group 3 comprised 25 to 45 kg body weight (n=17) and group 4 has 4 dogs having over 45 kg (n=4). Following the assessment of prospective analysis, 47 different diseases were detected in 100 patients. The most of dogs were diagnosed to have more than one disease. The detected diseases were classified according to the systems involved as; circulatory system (n=54), gastrointestinal system (n=21), urinary system (n=19), genital system (n=20), respiratory system (n=16), endocrinology and metabolism (n=15), lympho-reticular system (involving spleen and lymph node) (n=9), loco-motor and central nervous system (n=7), ear and hearing loss (n=4), and dermatologic pathology (n=2). Considering to the prevalence of diseases, the most commonly diagnosed ten diseases were; chronic valvular heart disease 22.81%, cardiomegaly 6.43%, mass in the lung 5.85%, pyometra 4.09%, mass in the mammary gland 4.09%, chronic renal failure 4.09%, cystitis 2.92%, pericardial effusion 2.34%, and diabetes mellitus 2.34%. [ABSTRACT FROM AUTHOR]