Transitory chronic morbidity of children aged 0-6 years from the town of Varna was retrospectively studied for a five-year period (1997-2001) based on the results obtained during the annual prophylactic examinations. A total of 54,068 children (24,204 being 0-3 year-old and the rest of 29,864 aged between 4-6 years) is involved in the study. Based on data from the documentation records the frequency of cases per 1000 examined is given. The structure and the dynamics of transitory morbidity is determined. The total chronic transitory morbidity for the whole period is 36 per 1000 examined children. The prevalence of chronic diseases in children aged 0-3 years is 23%@1000, while in children aged 4-6 years it is twice as high (47%@1000) (p < 0.01). In the nosologic structure of chronic morbidity in children aged 0-3 years diseases of the blood and haemopoiesis dominate (52.2%) followed by congenital anomalies (7.5%), and bronchial asthma (4.1%). For the age group of 4-6 years, diseases of the blood and haemopoietic organs occupy the first place (14.3%). Second come disorders in refraction, accommodation and vision (12.8%) followed by bronchial asthma (11.8%) and scoliosis (11.2%). The results obtained in this study define the priority guidelines of the work of general practitioners and medical specialists for disease prevention and health promotion in children aged up to 6 years. They are offered to the municipal authorities of public health.