Background: The main problem in emergency departments is relief of pain in patients with renal colic. The effect of fluidrestriction diet in reducing the colic pain is unknown. The present study was performed to investigate the effect of fluid restriction diet in reducing the colic pain.Materials and Methods: In this clinical trial, among patients with renal colic who had referred to Vali asser hospital of Birjand city, 141 patients who had inclusion criteria were selected and randomely divided into two groups (71 and 70 patients in each group). In the first group, diclofenac 100 mg suppositories, and aliter of normal saline solution for one hour; and in the second group, 100 mg diclofenac suppository alone was administered.Patients pain intensity, before treatment, 30 and 60 minutes after treatment, was measured using a visual analog scale pain scores (VAS). Data were analyzed using statistical software SPSS 15, and Chi-square, t-independent, Mann-Whitney U, Friedman and Wilcoxon tests.Results: The mean pain score, 30 and 60 min after treatment, was significantly greater in diclofenac with fluids group than diclofenac-only group. diclofenac with no fluid group (P<0.001).Although the mean changes in pain intensity, was greater indiclofenac-only group than diclofenac with fluids group (P=0.005), but the mean changes in pain intensity, 30 and 60 min after treatment, in both groups was not statistically different (P=0.32).Conclusion: The results of this study show that fluids uptakerestrictions, using a suppository painkillers such as diclofenac, can greatly reduce pain in these patients; and prevents the patients frequent refers to the emergency room to get a narcoticanalgesic