BACKGROUND: Refrigeration is the most common method of preservation for 24 hour urine collection. We tried to find out if the concentrations of the frequently measured chemicals in urine refrigerated for 24 hours were different from those in fresh urine. METHODS: The concentration of calcium, phosphorus, uric acid, creatinine, sodium, potassium, chloride, and protein was measured in fresh urine specimens for routine urine analysis. After refrigeration of the rest of the urine specimens for 24 hours, the same tests were performed, and the results of them were compared with those of fresh urine. Some urine specimens showed precipitation and decreased uric acid concentration after precipitation, and the chemical properties of them were determined statistically. RESULTS: The concentrations of the protein, phosphorus, creatinine, sodium, potassium, and chloride of refrigerated urine was not different statistically from those of the fresh one, but calcium and uric acid showed statistical difference between fresh and refrigerated samples (P<0.05). Urine specimens with precipitation and decreased uric acid showed chemical characteristics of high uric acid concentration and low pH. CONCLUSIONS: For the measurements of total protein, phosphorus, creatinine, sodium, potassium, and chloride, the urine can be refrigerated while collection of 24 hours, but additional procedure is recommended for the measurement of calcium and uric acid.