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Background: Pyelonephrities is the urinary tract infection. Using supplemental dugs may decrease duration of treatment and hospitalization. We studied the effect of vitamin C on the recovery of symptoms due to pyelonephrities Methods and Materials: In this clinical trial, double blind, study, 64 patients with uncomplicated pyelonephrities were assessed in 2 groups randomly. Case group took vitamin C capsules, and control group took placebo capsules. In both groups, primary treatment was ceftriaxon capsules during hospitalization and they took ciprofloxacin capsules for 14 days after discharging. Symptoms and Urinary analysis were assessed in the first day of administration and then on the 7th and 14th days after discharging. Data were analyzed with Chi-Square test. Results: Mean of fever duration in vitamin C group (1.130.34 SD day) and placebo group (1.560.62 SD day) significantly decrease (p=0.001). There was a significant difference in dysuria duration in vitamin C group 2.191.06 SD day with placebo group (2.971.06 SD day) (p =0.007). In flank pain, nausea and vomiting duration difference was not significantly (p≥ 0.05). Conclusion: It seems vitamin C, as a supplemental drug improves some pyelonephrities symptoms, such as fever and dysuria, decreases of the hospitalization period