The aim of the present diploma thesis was monitoring of physiological changes of basic parameters of blood count and selected biochemical parameters in puppies of Beagle strain depending on age in the range from two weeks to four months. The experiment involved 16 puppies (8 males and 8 females) of Beagle strain delivered from the monitored breed of laboratory dogs of the firm BioTest s.r.o., Konárovice. The blood count determination was performed by means of a hematology analyzer, and the following parameters were evaluated: erythrocytes, hemoglobin, hematocrit, mean volume of erythrocytes, hemoglobin of erythrocytes, mean corpuscular concentration hemoglobin in erythrocytes, thrombocytes and leukocytes. Subsequently, the differential count was determined microscopically from the total number of leukocytes. The hematological examinations were performed eight times altogether in the 2nd, 4th, 6th, 8th, 10th, 12th, 14th and 16th week of the animals’ age. Biochemical examination was performed in the 4th and 12th week of the puppies’ age and involved the values of urea and of the liver enzymes ALT and AST. The examination was conducted in the Department of Veterinary Sciences, Czech University of Life Sciences, Prague. The puppies’ body weight was also determined throughout the study, namely in two-week intervals from the 2nd to the 16th week of their age. All the findings obtained were evaluated statistically. The values of red blood count parameters of the puppies at the age of 2 weeks were close to the physiological values of adult dogs. In the next measurement performed, i.e. in the 4th week of the animals’ age, all the parameters exhibited a significant decrease, and the values gradually returned to the physiological values of adult animals from the 10th to the 16th week of age. The mentioned decrease in the blood count values was caused by physiological anemia of the puppies. The thrombocyte counts fluctuated only mildly during the monitored period, exhibiting no marked deviations from the values of adult dogs. The values of leukocytes and their differential count fluctuated mildly, remaining at the level of physiological limits valid for adult dogs. A distinct decrease in urea concentration in the puppies’ blood plasma was observed between the 4th and the 12th week of their age. In the same period, the activity of liver enzymes ALT and AST was significantly increased, but the two parameters did not go beyond the physiological range of adult animals. The curve of body weight showed an increasing trend corresponding to the age of the given dog strain. The obtained results of hematological and biochemical parameters monitor their physiological changes in the period from the 2nd to the 4th week of puppies of the Beagle strain, which was the aim of the present research work. The pre-stated hypothesis about the changes of the puppies’ hematological and biochemical parameters depending on age and gender was confirmed.