Background: Biopsy is an invasive method of taking tissue samples which are estimated microscopically. Oligobiopsy is performed in adults and children in the course of renal diseases, both in diagnostic process and in evaluation of treatment results. More precise sampling is possible when a biopsy is performed under ultrasound guidance. The aim of the study is to evaluate diagnostic effectiveness of renal ultrasound in cases of biopsies in children on the basis of analyses of histopathologic results, complications and learning curve assessed with relation to procedure duration. Material/Methods: In the Radiology Department in Zabrze, renal ologobiopses were performed in 174 children from the Pediatric Department, 88 girls and 86 boys. The age ranged from 4 to 19 years, mean 12 years. The biopsies were performed under general anesthesia with an automatic "gun" under ultrasound guidance. Results: Biopsy effectiveness was estimated after the diagnostic material was collected. Our material included 22 samples with less than 6 glomeruli (12.6%), only in 6 children (3.5%) the final diagnosis was not established (including 2 samples without tissue material). Minor complications accounted for 65.5% of all biopsies and major ones 3.4%. A statistic correlation between the procedure duration and the date of examination was found; no correlation between the date and the number of glomeruli in a sample was discovered. Conclusions: The value of ultrasound examination in renal biopsy in children is very high. The percentage of complication is low, which makes the procedure safe. The biopsy duration depends on the examiner's experience, and the number of glomeruli on the degree of renal disease advancement.