Basic indicators of renal function include assessment of glomerular filtration. To this end indirect methods are used among which the most widely used is creatinine estimation which is however intluenced by a number of factors. Assessment of creatinine clearance is often based by an error of urine collection. As a suitable indicator which does not burden the patient, in particular Children, recently assessment of the cystatin C serum level is reported. The authors compare three variables: the creatinine and cystatin C blond level and the glomerular filtration rate in a group of Children aged 0 - 1 year and 1 - 17 years in patients with chronic renal failure, chronic renal disease and in a control group. By statistical evaluation using 5tudent's non-paired t-test and correlation regression analysis they proved in patients under 1 year with diseases of the urinary tract and in the control group cystatin C and creatinine values at the significance level of p < 0.01 and a weak positive correlation of cystatin C with the creatinine value (r = 0.735, p < 0.01). They conclude that assessment of cystatin C, taking finto account the creatinine value provides satisfactory information of glomerular filtration and can be used with advantage where urine collection for assessment of clearance of endogenous creatinine would be difficult e.g. in young Children and non-cooperating patients.

        Key words: glomerular filtration, cystatin C, creatinine, childhood