OBJECTIVES. To estimate cellularity of the urine sample depending on the duration of natural sedimentation - 15 minutes after sampling and 2 and 4 hours after sampling. To estimate the prevalence ofdegenerative changes in urothelial cells 15 minutes after sampling and 2 and 4 hours after sampling. To determine the optimal time of natural sedimentation of the urine sample with regard to cellularity and the prevalence of degenerative changes. STUDY DESIGN. A cross-sectional study. PARTICIPANTS AND METHODS. A cross-sectional study included 84 respondents (52 men and 32 women) who were referred to the Department of Clinical Cytology, University Hospital Center Osijek, for cytodiagnostic urine sedimentation testing within four weeks todetect the presence of malignant cells. RESULTS. There are no significant differences in cellularity and the prevalence of degenerative changes regarding the duration of natural sedimentation. Women havea significantly higher number of plate cells in samples than men. Hematuria occurs in 28% of respondents, whose cellularity is significantly higher in samples after 2 hours and after 4 hours of natural sedimentation. Patients with hematuria do not exhibit significantly more pronounced degenerative changes in samples after 15 minutes and after 2 and 4 hours. Pronounced infection occurs in 21% of respondents who also have a significantly higher cellularity in samples after 15 minutes and after 2 and 4 hours of natural sedimentation. Respondents who have changes associated with infections also have significantly more pronounced degenerative changes in the sample after 15 minutes, after 2 hours and after 4 hours. CONCLUSION. Natural sedimentation of urine samples with the aim of increasing the cellularity of the sample for cytological examination should not last longer than fifteen minutes, since the cellularity of the sample does not increase during its prolonged storage. The delay in the processing of urine samples can be extended to four hours, as the prevalence of degenerative changes does not significantly change in that time interval. KEYWORDS. cellularity; urine; degenerative changes; sedimentation